NEW YORK (AP) _ Thirteen police officers at one precinct have been suspended without pay for alleged involvement in a corruption scheme that a police source said involved extorting money from drug dealers.

The suspensions, announced Tuesday, officially charge the officers from the 77th precinct with conduct unbecoming an officer.

Authorities would not say what prompted the suspensions pending a grand jury investigation. But a high-ranking police official, who spoke only on the condition of anonymity, said the officers were suspended for shaking down drug dealers in Brooklyn.

Mayor Edward I. Koch said the problem came to light in April 1985 and was turned over to the police internal affairs division and subsequently to a special prosecutor.

News of the latest scandal involving city personnel leaked out Tuesday afternoon and police brass moved to find and immediately suspend the officers involved.

Some were called back from patrol and ordered to turn in their guns and badges, and others heard about it from news media reports. ''They hadn't even been told,'' Richard Hartman, a lawyer for the Patrolmen's Benevolent Association, told The New York Times.

WCBS radio and the New York Post said the alleged corruption involved shaking down dealers specializing in the potent form of cocaine known as crack.

The Post quoted unidentified sources as saying the officers would take cash and crack from the dealers, keep the money and sell the drugs.

''I would characterize it as a criminal investigation into a particular precinct,'' special Prosecutor Charles J. Hynes said in declining to confirm or deny the reports.

New York Newsday said a dealer arrested in February began cooperating with Brooklyn District Attorney Elizabeth Holtzman's office and was rigged with a recording device.

Two officers were given a chance to gather evidence or go to jail, WCBS, the Post and Newsday said, and they also wore hidden microphones during the investigation.

The Times, quoting unidentified law-enforcement source in today's editions, said the suspended officers and others still under investigation went to drug sites during their off hours.

One official quoted by the Times said there was ''no organized ring'' involved.

Those suspended included a sergeant, said spokeswoman Sgt. Diane Kubler. The precinct has 17 sergeants and 205 officers.