Several defendants face charges in connection with murders and robberies at Manhattan bars that terrorized the city’s gay community, according to three people with knowledge of the matter.

The homicides last spring drew wide attention to a danger that has long stalked New York’s nightlife: the use of easily obtainable drugs to incapacitate, rob and sometimes kill.

John Umberger, 33, and Julio Ramirez, 25, were killed after they left bars in Hell’s Kitchen in what the medical examiner’s office ruled were murders committed in the course of “drug-facilitated theft.”

After they died, the families of both men discovered that large amounts of money had been stolen from their financial accounts. Their assailants had unlocked their phones using facial recognition. As public knowledge of the killings grew, more victims came forward to say they too had been drugged at gay bars in New York, and then robbed and left for dead.

The police department has said it is investigating a pattern of similar crimes at both straight and gay bars, and that the victims have been a mix of heterosexual and L.G.B.T.Q. people. Detectives believe more than one group may be involved in the crimes, according to two of the officials with knowledge of the investigation.

Last week, the police said the July death of Kathryn Marie Gallagher, a fashion designer who worked with Lady Gaga, Laverne Cox and other high-profile clients, was also a drug-related homicide that may have been part of an attempt to rob her.

The crimes have had a singular impact on the city’s gay community, which emerged from the pandemic to face a monkeypox outbreak, economic turmoil that threatened many bars that serve as de facto community centers, and an increasingly hostile national political climate.

The deaths of Mr. Umberger and Mr. Ramirez spread fear and rumors among many who frequent those bars and community spaces, and also started a larger conversation about similar attacks at gay nightlife venues.

The Police Department said Wednesday that no arrests had yet been made in connection with the murders, though charges have been proffered, and the Manhattan district attorney’s office said it could not comment.

Investigators had remained tight-lipped throughout the nearly yearlong investigation, which hinged on complex but ubiquitous technology, online banking, and so-called date rape drugs that are essentially undetectable.

The only suspect so far identified is Andre Butts, 28, who the police said had been charged in June, accused of using Mr. Ramirez’s credit card to buy two pairs of Nike sneakers for $544.38 just hours after he died. A lawyer for Mr. Butts, Terrence J. Grifferty, did not respond to a request for comment on Wednesday.

The charges came almost one year after the body of Mr. Ramirez, a social worker from Queens, was abandoned in the back of a taxi on the Lower East Side by a group of men he met that night at Ritz Bar and Lounge in Hell’s Kitchen, his family said. He was declared dead at a hospital roughly 90 minutes after he left the bar. After he died, his family discovered money had been removed from his bank account.

The following month, Mr. Umberger, a political consultant visiting New York City from Washington, D.C., went missing after he visited the Q, a nightclub on Eighth Avenue around the corner from the Ritz.

His body was found five days later in the townhouse where he had been staying on the Upper East Side, and more than $20,000 had been taken from his accounts after his death, said his mother, Linda Clary. She said surveillance video showed two men leading her son into a waiting car outside the club.

The New York Times interviewed more than a dozen other men who said they had been drugged and robbed in a similar fashion at bars in Hell’s Kitchen, Chelsea and the East Village since 2020. The men believed they had been incapacitated with GHB or another so-called date rape drug. At least one said his doctor suggested to him after he was attacked that GHB had been used.

The men also said they had been reluctant to file reports, or had done so and been treated dismissively by the police. Investigators initially told the families of Mr. Ramirez and Mr. Umberger that they viewed their deaths as accidental overdoses, relatives said.

This month, the New York City medical examiner’s office said Mr. Ramirez and Mr. Umberger were killed by similarly powerful mixtures of cocaine, fentanyl and other drugs.

The medical examiner’s report did not find any so-called date rape drug, or roofie, in either man’s system. Medical experts say such substances are difficult to detect because they stay in a person’s system only a short time.

Most routine drug and toxicology tests do not look for GHB, according to the Justice Department. It is easily obtainable in New York and used recreationally in small doses by some gay men.

Last year, the police arrested several men in connection with a series of similar robberies at Manhattan bars that cater to a primarily heterosexual clientele. Court documents indicated one of those men was also accused of stealing $2,000 from a patron of the same gay bar at which Mr. Ramirez was last seen alive.

In December, Alvin L. Bragg, the Manhattan district attorney, announced the indictment of another man, Kenwood Allen, on murder, robbery and other counts in a series of drug attacks on the Lower East Side in which five people were robbed and two were killed.

Maria Cramer and Chelsia Rose Marcius contributed reporting.