Mayor Marion Barry admitted that visiting an acquaintance suspected of drug involvement "caused some embarrassment" for the city but said he was innocent of wrongdoing and would be "extra, extra careful" to avoid appearances of impropriety in his personal life.

The city's U.S. attorney, meanwhile, said Thursday that his office had decided to conduct a full investigation of the incident, in which the mayor visited a former city employee at a Washington hotel just as police were preparing to attempt an undercover drug buy from the man.The Washington Post, in Friday's editions, quoted an unidentified source as saying the FBI may join the federal investigation.

Police have turned over to U.S. Attorney Jay B. Stephens results of an internal probe into why two detectives were stopped from attempting a drug buy from former city employee Charles Lewis after Barry turned up at Lewis' hotel room. The incidence occurred a week ago.

Earlier this week, federal prosecutors had said only that they were reviewing what police investigators had found. But on Thursday, Stephens said his office "is conducting a full investigation of this entire matter."

Barry, through spokesmen, has repeatedly denied any wrongdoing. On Thursday he called a news conference to answer questions "around the controversy" and he vigorously denied using or seeing drugs in the hotel room.