After a parking garage collapsed in Lower Manhattan last month, killing one person and injuring five others, officials scrambled to check dozens of other garages across the city for structural problems that could cause another disaster.

They immediately identified dozens of garages with potential hazards, ordering some shuttered and closing off sections of others until their structural defects could be repaired.

Three weeks after the fatal collapse, city officials have revealed little about what they found in their sweep. They have not identified the more than 170 parking structures they rushed to inspect or divulged what conditions they discovered within them.

But a New York Times examination of the city’s garages has found that serious structural problems are widespread — and in many cases have been allowed to persist uncorrected for years. Reporters analyzed millions of rows of data on building inspections and violations, interviewed structural engineers and former city officials and reviewed Buildings Department records, and identified more than three dozen garages across the city that have been cited recently for crumbling ceilings, exposed and rusting reinforcing bars and other defects.

At one garage on Manhattan’s Upper West Side, an inspector touring the structure earlier this month happened across a 12-inch-by-18-inch chunk of concrete that had fallen from the building’s ceiling, city records show. Even so, that parking structure — like nearly all of the other garages identified by The Times — remained in operation last week, not subject to any city evacuation order.

More than 20 garages have been cited for violations that suggest they were sometimes exceeding their capacity, a practice that was under investigation as a possible factor in last month’s collapse. In at least six cases, inspectors found so many cars packed into a garage that exits on several levels were completely blocked, the records show.

Another two dozen garages had open enforcement cases pending against them for years without any apparent follow-up. Inspectors visited them again only after the April 19 collapse at 57 Ann Street, raising questions about the effectiveness of the city’s code enforcement practices.

The Ann Street garage itself had several outstanding violations that appeared never to have been corrected before the collapse, including a case from 2003 in which inspectors cited the building for cracked, degraded and defective concrete. A representative of the company that operated the garage, Little Man Parking, did not respond to requests for comment.

In interviews and statements, owners and operators of other garages defended the safety of their structures, playing down the hazards documented by city inspectors or saying the Buildings Department’s records were inaccurate.

City officials did not respond to questions about the inspection and enforcement process or explain why some garages were allowed to continue operating despite being flagged for structural problems.

The officials have yet to determine what caused the collapse on Ann Street or say how many cars the garage was holding when its concrete failed. Pictures and video from the scene showed dozens of cars and S.U.V.s on its roof when it gave way.

Records show there were more than 300 multistory garages operating across New York City last week. A spokesman for the Buildings Department, Andrew Rudansky, said inspectors had visited 187 garages since the collapse, ordering three shut completely and sections of 12 others closed off until they could be made safe. He said inspectors also cited other garages for violations of city codes but declined to say how many or how serious the violations were.

Until this year, owners of parking garages in the city were not mandated to have professional engineers inspect their structures and file reports to the Buildings Department. That changed with a local law enacted in 2021 that requires owners of garages in Lower Manhattan, Midtown and on the Upper West Side to start those reports by the end of this year. For garages in the rest of Manhattan and Brooklyn, the deadline is Dec. 31, 2025. Those in the Bronx, Queens and Staten Island have until the end of 2027.

Without mandated inspections, violations were caught by the city only if work was being done on a garage or a proactive owner hired an engineer to assess conditions, inspectors said. Some violations were the result of a complaint called into the city’s 311 line. But it would be difficult for customers to learn of deteriorating conditions in most garages because access to upper levels is restricted to garage employees.

The Buildings Department shuttered a garage under an apartment building on East 80th Street on the Upper East Side only after an engineer hired by the owner reported unsafe conditions there, according to a report. City inspectors found water damage to the foundation walls and determined that the entrance ramp was “no longer structurally stable,” the report said.

Mark Levine, the Manhattan borough president and a sponsor of the inspection legislation as a member of the City Council, said the deadlines for the first round of inspections were stretched out to give the Buildings Department time to process them. But now, in the wake of the Ann Street collapse, he said he thought the inspection process “should definitely be accelerated.”

Mr. Levine suggested that all of the city’s oldest garages, no matter their location, ought to be required to have thorough inspections by the end of the year.

“It’s time to put into place greater protections,” he said.

Some engineering experts said such requirements were overdue.

“It couldn’t have happened soon enough. There are a lot of buildings with issues,” said Muhammad Rahal, a structural engineer certified by the Buildings Department to conduct parking garage inspections. “A lot of things will be discovered.”

Mr. Rahal, who has been inspecting buildings for 20 years, said it was only a matter of time before a garage collapse happened like the one on Ann Street “given the number of buildings of that age that are supporting a lot of vehicles.”

“I just hope that now more of these building owners will take it more seriously,” Mr. Rahal said.

The garage that collapsed on Ann Street last month was nearly 100 years old, but it was not unique in that regard.

The Times identified more than 40 multistory parking structures across the city of the same age or older, including some that were originally used to hold carriages and the horses that pulled them.

A building’s age is not always an indicator that it is in poor condition. One of the oldest garages in the city, a five-story building at West 75th Street and Amsterdam Avenue that was designed in 1888 as the New York Cab Company Stable, had no open enforcement cases on file for serious violations.

Others, though, have been cited for structural weaknesses and other hazardous conditions. City records show that more than a dozen of the city’s oldest garages have been flagged for such violations, but the records do not include proof that the problems were ever corrected.

The 117-year-old Monterey Garage, on West 89th Street, is a prime example. City records show that it had an open violation from 2005 for bricks in its facade that were “loose, skewed and bulging.”

After the Ann Street collapse, an inspector found a large chunk of concrete that had fallen from a ceiling and been left on the floor and steel in the cellar of the five-story building that was “fully deteriorated,” the inspector reported. But the Buildings Department allowed the garage to continue operating, according to its records.

The owner of the Monterey Garage, Kenny Mance, said it was “in the same condition it was in 40 years ago.” He said the serious violations had been found in a utility room beneath the lowest parking level and would be repaired after an assessment by an engineer this week.

City officials have documented similar problems in other aging garages but allowed them to continue operating, in some cases for years.

At a 113-year-old garage on Charles Street in Greenwich Village, records show that officials observed cracked ceilings and exposed rebar on every level along with 18 other violations dating to 1988 but documented no evidence that any of the problems had ever been addressed.

When a city inspector visited the garage earlier this month, the inspector found crumbling ceilings, “excessive rust” and cracks in the walls on the third level, records show. A representative for the company that operates the garage, Impark, did not respond to a request for comment.

A 101-year-old garage on West 181st Street in Washington Heights still had open enforcement cases dating back to 2006 and had been subject to a partial evacuation order since 2012, when a city official discovered 10 cars parked on a roof that was not approved to hold them. Records show the inspector was denied access to check conditions on the roof during a visit in 2021.

David Saperstein, the operations manager for the building’s management company, Park It, said the city’s records were outdated and did not reflect the steps the company had taken to comply with the order. He added that the roof was cleared of cars the day after the vacate order was issued.

A third garage — a five-level structure on Chrystie Street in Chinatown that was built in the 1920s — had three open enforcement cases for crumbling concrete, cracks on the roof and other violations when an inspector visited it on May 2 and discovered more structural flaws, including exposed steel beams and reinforcing bars on every level, records show. A representative of the company that owns the garage, MTP Investment Group, said it had hired an engineering firm to address the inspector’s findings but termed them a “cosmetic” issue.

One common trait among the city’s oldest buildings was the use of a type of concrete that is especially susceptible to deterioration if not properly maintained.

It was made from cement mixed with cinders from steel furnaces, said Dan Eschenasy, the former chief structural engineer for the city’s Department of Buildings and its Department of Design and Construction. The cinder concrete was lighter, and probably cheaper, than concrete made with gravel, so it was used for floors and roofs, Mr. Eschenasy said.

But cinder concrete is more porous than stone concrete, making it more vulnerable to water and salt, which cars carry into garages. As water and salt seep into concrete, they can corrode the metal reinforcements, making them expand. That pressure can cause the surrounding concrete to spall — or crumble — often the first sign of the underlying structural problem.

Even old cinder concrete can remain sturdy when maintained and protected from the elements, Mr. Rahal, the inspector, said. He said he had often found that a lack of weatherproofing of concrete slabs could allow water to seep in and lead to serious structural damage.

Without a protective layer or waterproofing, Mr. Rahal said, “water and salt will get into that concrete slab and turn that slab into mush.”

He said he saw those effects especially when inspecting structures built in the 1920s, when garage construction boomed as cars became more popular.

“They’ve got bad spalls, they’ve got reinforcement that’s corroded,” he said. “It’s all because the owner didn’t maintain the building properly.”

Structural problems were not contained to the oldest parking buildings in the city, The Times found.

An analysis of city data spanning more than 18 million enforcement actions showed that more than 175 garages had recorded at least one violation of the city’s building code over the past 20 years.

About 130 of the parking structures had been cited two or more times for hazardous conditions or packing in more cars than were allowed.

The records also offered hints of what city officials were finding in the aftermath of the Ann Street collapse.

On May 1, an inspector visited the two-level garage under the 36-story Trump Plaza, an Upper East Side apartment building developed by Donald J. Trump in the mid-1980s, and found “a state of disrepair,” with chunks of concrete missing from the ceiling and signs that water had penetrated the walls.

A man who identified himself as the manager of the Trump Plaza garage referred questions to the garage operator, Enterprise Parking. A representative of Enterprise did not respond to a request for comment.

When the Buildings Department announced on April 28 that it had found unsafe conditions in four garages and ordered them to be emptied out partially or completely, two of them were beneath fairly modern apartment buildings.

The garage at 225 Rector Place, where inspectors found “extensively corroded” concrete and spalling on the underside of two ceilings, is in the lower levels of a 25-story residential building erected in 1986. The Buildings Department ordered sections of the garage be closed off until they could be repaired.

The Buildings Department also ordered that parts of the garage under an eight-story apartment building at 50 Bayard Street in Manhattan be closed off for repairs after finding “numerous severely deteriorated and rusted steel beams, with excessive cracked and spalling concrete piers in various locations.” That building is 61 years old.

In early May, the Buildings Department followed up on a tip from a television reporter and found unsafe conditions, including support columns either missing or corroded, in a garage at 143 West 40th Street, near Times Square. That discovery provoked an order for the immediate closing-off of parts of four levels of the nine-story structure, Mr. Rudansky said.

The 40th Street garage, like the one on Bayard Street, is managed by Icon Parking, which says it is the biggest garage operator in the city, with more than 200 locations. A company spokesman, Ed Tagliaferri, said the firm was working with the Buildings Department and its landlords to ensure its garages were safe.

Among the factors officials are investigating in the Ann Street collapse is whether the building’s roof deck was overloaded at the time of the failure. If the parking structure was over its capacity, it would not have been an outlier among the city’s garages, records and interviews show.

With parking rates as high as $50 a day and exceeding $1,000 a month in more crowded parts of the city, garage owners have an incentive to squeeze as many cars into their structures as possible. The quest to maximize profits has motivated owners to overstuff their garages, in some cases by adding lifts without the proper permits.

The Times found at least 25 garages with violations related to excess occupancy or the installation of lifts without a permit. Lifts allow garages to stack one car above another, possibly doubling the number of cars they can hold, but also adding significantly to the load their structures must bear.

The Ann Street garage was cited in 2009 for exceeding its stated capacity and in the following year received permission to install 34 lifts, according to city records. The license for the four-level Ann Street garage indicated that its stated capacity was 276 vehicles.

As inspectors continued their enforcement sweeps, the Buildings Department was using “every tool at our disposal to protect the public,” the agency’s spokesman, Mr. Rudansky, said. But, he acknowledged, there could be dangerous conditions that have not yet been addressed.

“Lack of proper maintenance and regular repairs at these aging structures has in many cases led to severe structural hazards that endanger anyone who steps inside these buildings,” he said.