A sergeant in the city’s police department was arrested today in Long Island for aiding a drug dealer and lying to investigators, officials said.

Sergeant Roosevelt Green is accused of providing the leader of a Suffolk County crack cocaine ring, Frank Wilson, with information regarding surveillance vehicles being used by the Drug Enforcement Administration to track Mr. Wilson during spring of last year, according to the complaint filed in United States District Court.

A task force of city and federal law enforcement began an investigation into Mr. Green’s activities after DEA agents intercepted several incriminating phone calls between him and Mr. Wilson in March, according to the complaint.

Agents overheard the two talk about running license plates on several cars that were being used to investigate Mr. Wilson.

The city’s police department joined the investigation and discovered that Mr. Green used an access number belonging to his partner to run the plates through a database operated by the FBI, according to the complaint.

When DEA agents questioned Mr. Green for the first time, he acknowledged knowing Mr. Wilson but denied giving him any information about license plates, according to the complaint. After further interrogation, Mr. Green said he didn’t remember providing Mr. Wilson with information.

Mr. Green was arraigned today in Central Islip, Long Island on charges of unlawfully accessing a computer and providing false information.

Mr. Wilson and at least a dozen other members of his organization have been indicted on drug charges.