FBI agents on Thursday spent several hours gathering documents at the downtown offices of Ronald A. White, an attorney who has raised money for Street, performs legal work for the city and specializes in helping clients win government contracts.
Agents also seized records from the city's finance department and the Board of Pensions and Retirement, according to City Solicitor Nelson Diaz.
Street declined to say specifically what information the agents had requested, but said the documents covered a range of city functions.
"Looking at the requests, it is virtually impossible to know what they are looking for," said Street, who has repeatedly denied any wrongdoing.
FBI spokeswoman Linda Vizi declined to comment on the raids or say whether they were related to the bugging of the mayor's office.
A federal official, speaking on condition of anonymity, has told The Associated Press that Street is a "subject" in an FBI probe. The legal term is used to describe a person whose conduct is within the scope of a criminal probe, although they themselves may not be suspected of breaking the law.
White refused to comment to reporters Thursday as he left his office in the middle of the FBI's search.
Over the past few months, federal agents have requested thousands of pages of records related to city contracts, questioned members of Street's administration and sought information from companies that bid for city work.
The FBI also secretly planted listening devices in Street's City Hall office — an operation that became a fiasco when police officers, unaware that a probe was under way, discovered the bugs during a routine security sweep Oct. 7.
The discovery of the listening devices prompted quick moves by federal agents to seize evidence in the case. The day the bugs were found, conducted several searches and raided a financial firm run by Street allies that had obtained a no-bid city contract, according to the Philadelphia Inquirer.
In the days since the bugging was uncovered, agents also have taken records from the city's Minority Business Enterprise Council and searched the offices of a debt collection agency that has done work for the city, and whose owner, an influential Philadelphia imam, campaigned for Street and was on his transition team in 1999.
It is unclear whether any of the investigations are related.
Street's administration has faced a series of charges of wrongdoing, according to The New York Times, involving forgiving parking violations by allies, a multimillion dollar contract that was awarded to a firm connected to Street's brother and a mayoral aide's alleged threat to a landlord who rented space to the opposing campaign.
Street, a Democrat, has called the timing of the investigation "suspicious," considering that he is in the final weeks of an election campaign against Republican businessman Sam Katz. Justice Department officials deny any political connection.
Street beat Katz four years ago by fewer than 10,000 votes in this city of 1.5 million.
Last month, polls showed a dead heat. But despite the federal probe, the Inquirer reports that a Temple University/CBS3/KYW-AM survey of 427 voters between Oct. 9 and Oct. 15, found Street with 48 percent support from likely voters, versus 41 percent for his opponent.
The race had turned nasty well before the bugs were found. Supporters of Street, who is black, and supporters of Katz, who is white, have accused each other of race-baiting.
In August, someone tossed what was believed to have been an unlit firebomb through the window of a Katz campaign office. An aide to Street and a former city employee were charged with making threats after getting into a confrontation the same day.
The Katz campaign has filed a private criminal complaint accusing Street of refusing to return $125,000 in campaign donations it claimed were improper.