New York City has drastically reduced the number of criminal cases it pursues over serious fire safety violations, a review of court data shows, prompting worries about the rigor of its fire prevention strategy just months after a devastating fire killed 17 people in a Bronx high rise.

After the pandemic hit in March 2020, the closure of criminal courts led to a precipitous drop in the number of cases being filed every month. But the sluggish pace held even when courts reopened, and even after city leaders publicly pledged to crack down harder on fire safety violations following the January blaze in the Bronx.

Compared with the roughly 9,800 criminal cases filed on average every year in the decade leading up to the pandemic, there were fewer than 200 in 2021, amounting to a more than 98 percent reduction, according to court data. As of mid-September this year, the number was just over 200.

In responses to emailed questions, city officials did not dispute the decline in criminal prosecutions. They said fire inspectors were directed in September 2020 to pursue lesser, civil charges in many cases, so that they could be quickly processed in an administrative court that remained open during the pandemic.

A spokeswoman for Mayor Eric Adams said in a statement that focusing on civil charges was the best way to keep New Yorkers safe, adding that the city had stepped up fire safety outreach after the Twin Parks blaze and directed city agencies to share information on violations.

“With criminal courts severely backlogged as we come out of the pandemic, continuing to issue criminal summonses for all infractions would be unwise and risks further delaying when serious infractions can be heard,” she said.

The number of people killed in fires has decreased dramatically in New York City in recent decades, and the city’s fire prevention efforts have typically been held in high regard. But the January fire in the Bronx, at an affordable housing complex, Twin Parks North West, was one of the deadliest in decades and underscored how lower-income and immigrant communities remain disproportionately exposed to fire danger.

The city has traditionally prosecuted property owners and businesses such as hotels and restaurants in criminal court when lesser penalties for safety hazards are ignored. New York also pursues criminal cases when a problem — say, a locked exit or improperly stored flammable material — presents a significant danger.

The decline in this muscular form of fire code enforcement, however, comes as the Bronx fire has prompted the city to confront broader problems in fire safety oversight. That system has long been run by a jumble of agencies and has not always been effective at swiftly addressing fire hazards.

Representative Ritchie Torres, a Bronx Democrat whose district includes the Twin Parks high rise, called the decline in criminal cases an “alarming abdication of fire code enforcement in America’s largest city.”

“The need for rigorous fire code enforcement is no abstraction to me,” he said. “It is a matter of life and death.”

Councilwoman Joann Ariola, a Republican who chairs the Committee on Fire and Emergency Management, said she had been aware of the downturn and is “looking at several avenues to remedy” the situation, attributing the trend in part to a “manpower strain” at the Fire Department.

A spokesman for the department, Frank Dwyer, said that between 2020 and now, inspectors had written more than 700 criminal summonses — as the violations are known — for serious problems that had not yet been filed in court because of a backlog. The city can only file about 20 cases a month, because the court has not reopened to “full capacity,” he said.

But a spokesman for the court system, Lucian Chalfen, said the city could file more cases if it wanted to, adding that the reduced number was due to an issue with the Law Department, which represents the city in fire code cases.

“It has nothing to do with us,” he said.

The Law Department said criminal prosecution is relatively slow because of “burdensome discovery requirements.” Nicholas Paolucci, a spokesman for the department, said it was working with the Fire Department to tackle the “most egregious cases.”

It is difficult to measure how many cases are now being filed in administrative court that would have been filed in criminal court in the past. Mr. Dwyer declined to provide examples of such cases. Administrative court data shows a modest overall decline in the number of fire code cases since 2020.

Before the fire at Twin Parks, fire deaths in New York City were at some of the lowest levels in years. In 1970, an era when fires scorched large swaths of the Bronx, 310 people died in fires in the city, not including firefighters. Between July 2019 and July 2020, that number was 53.

New York City has become known as “the world’s pace setter” in preventing fires, said Denis Onieal, a former deputy U.S. fire administrator who advises fire departments around the world. But new questions about fire safety in the city reflect conversations that have emerged after deadly blazes in other major cities like Chicago and Philadelphia.

Because of the Twin Parks fire, the tally of fire-related deaths in New York City between July 2021 and July 2022 rose to 92, the highest in four years. The rate of “serious fires” has also been on the rise.

After the Twin Parks fire, housing advocates and residents of the high rise described longstanding problems with fire alarms and doors. Some of those issues had been known to city and state officials before the blaze.

Officials with the union that represents fire inspectors said that many of the roughly 400 inspectors who work for the Bureau of Fire Prevention were diverted in 2020 to make sure restaurants were not serving meals indoors and that bars were checking vaccination requirements.

“Our city does not have enough fire protection inspectors within the F.D.N.Y. to fulfill the needs of this big city in guaranteeing that the buildings within it are safe,” Oren Barzilay, president of the union, testified at a hearing in April.

Mayor Adams has yet to name a permanent fire commissioner, with Laura Kavanagh serving on an interim basis since February. And the Fire Prevention Bureau has also seen turnover recently. Two top chiefs were reassigned to a department dealing with day-to-day operations in August.

It is not yet possible to know what kind of impact the decline in fire code prosecutions may have on the city. Criminal cases were in many instances a last resort, after other oversight systems failed to get results.

Fire safety in New York City is regulated by multiple agencies, including the Department of Housing Preservation and Development, the Buildings Department and the Fire Department. These agencies have not always communicated effectively, and the experiences of New Yorkers who have lived through fires or tried to get fire safety problems fixed illustrate how the system outside of criminal court can be confusing and ineffective.

Dora King used to rent an apartment in a five-story building just north of Central Park, before a fatal fire broke out last year. For years, housing inspectors had issued violations stemming from problems with smoke detectors, including in April and February of 2021, and from faulty self-closing doors.

One late night last November, Ms. King, 57, heard cries for help. She looked out her peephole and saw smoke pouring into the fifth-floor hallway from the stairwell. A fire had erupted on the third floor.

She fled through a window of her apartment, but found the fire escape ladder jammed at the second floor.

“All I could hear was the fire and the windows breaking,” she said. “I jumped.”

Ms. King said she suffered an ankle strain and had to undergo months of physical therapy.

Three people died, including a woman and her 3-year-old child.

According to the Fire Department, the people who died lived in apartments above where the fire started. One apartment did not have a smoke alarm, and officials were not able to determine if the alarm in the other was working.

Doors to common areas remained open on the night of the fire, said Sheena Morrison, who has lived in the building for 27 years, allowing smoke to billow through stairwells and into different floors and to choke off exits. She said there were no fire extinguishers or alarms in the hallways before the fire.

“Everyone was alerted by screams,” Ms. Morrison said.

She said tenants should not have to be on the lookout for every potential problem.

“Is the fire escape working?” she said. “That’s what the city does.”

The Fire Department and the Buildings Department conduct inspections of fire escapes triggered by complaints from residents, and the Housing Department checks on smoke detectors. But much of the responsibility for maintaining a building’s fire safety ultimately lies with its owner.

In Bushwick, Lyric Thompson, 54, has complained for years about gaps around the edges of the front and vestibule doors leading both into her apartment building and into an adjoining building. If a fire broke out, Ms. Thompson said, smoke could fill the front entrance area, blocking residents from exiting safely.

Various city agencies have repeatedly flagged problems with the doors, opening and closing multiple cases over the last several years, but the issues have persisted.

Since 2016, Housing Department inspectors have issued at least nine violations, often explicitly saying the doors are not fireproof and identifying problems with gaps. And since 2019, the Buildings Department has issued four violations related to the fire safety of the front door, and the building owner has twice paid a $625 fine, records show.

In May and again in August, the Fire Department issued its own violations for the building relating to “fire-rated doors.”

In response to questions about the building, Bushwick Holdings Group, Ms. Thompson’s landlord, said through a lawyer that it wanted to fix the problems with the doors, and said the Housing Department had installed one of the faulty doors. The Housing Department denied installing the door.

The city has never sought to prosecute Bushwick Holdings in criminal court, and the gaps around the doors remain.

“The system doesn’t function,” Ms. Thompson said.

Raúl Vilchis and Dana Rubinstein contributed reporting. Kirsten Noyes contributed research.