The discovery of a listening device in Mayor John F. Street's (search) City Hall office has touched off a political furor just weeks before Election Day and raised strong suspicions that the bug was planted by the FBI as part of a criminal investigation.

Pennsylvania Gov. Ed Rendell (search) on Wednesday called on the FBI to tell the public what it knows about the eavesdropping equipment, found Tuesday.

"I think given this extraordinary situation with four weeks to go in the campaign, it is incumbent upon the FBI to say why they planted the device," said Rendell, a Democrat like the mayor.

The bug was found during a routine sweep of Street's office by police. Street is a locked in a bitter rematch against Republican businessman Sam Katz (search), and the campaign has been marked by charges of threats and race-baiting. Election Day is Nov. 4.

FBI spokesman Linda Vizi said the equipment was not connected to campaign espionage, but she refused to say whether Street was being investigated or whether the FBI planted the device. She also would not comment on how the FBI was able to conclude so quickly that the device was not connected to the mayor's race.

At a news conference Tuesday evening, Street said: "I want to assure the people of this city that this mayor is not being investigated. I have done nothing wrong."

Street's campaign suggested the bugging was instigated by the Bush administration Justice Department for political reasons.

"What the campaign does find incredibly curious is that the FBI could so quickly leap to the conclusion that this was not related to the mayoral campaign in any way, shape or form," said Street campaign spokesman Frank Keel. "The timing of the discovery of these listening devices seems incredibly strange, seeing that we are four weeks out of the election, and we have a Democratic mayor ahead in the polls, and we are on the eve of the first mayoral debate."

Keel went on: "Do we believe that the Republican Party, both at the federal level and state level, is pulling out every stop to get Pennsylvania in 2004? Absolutely. Is the Republican Party capable of dirty tricks? I think that is well documented."

U.S. Attorney Patrick Meehan, the top federal prosecutor in Philadelphia, declined to say what federal agents might know about the bug, but denied politics plays any role in his office's decisions.

"The U.S. Attorney's office in the Eastern District of Pennsylvania has a long and proud history of doing its work without regard to partisan politics. That was the practice of my predecessors, and it is my practice as well," Meehan said in a statement.

Philadelphia Police Commissioner Sylvester Johnson said he turned the matter over to the FBI. He said the security sweeps of the mayor's office have been going on for decades.

An aide to Street, who spoke on condition of anonymity, said that more than one microphone was found and that all were within the mayor's office suite. Officials would not say how long the equipment was believed to have been in place. But police said a sweep done in June found nothing suspicious.

Katz called the discovery "breathtakingly shocking." His campaign denied having anything to do with the bugging.

Street beat Katz four years ago by fewer than 10,000 votes in this city of 1.5 million. Polls also show a neck-and-neck race in this year's campaign.

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. Supporters of Street, who is black, have accused supporters of Katz, who is white, of race-baiting.

Philadelphia city prosecutors had nothing to do with the bugging, said Cathie Abookire, a spokeswoman for District Attorney Lynne Abraham.