Mayor John Street, a Democrat, is locked in a bitter rematch against Republican businessman Sam Katz, and the campaign has been marked by charges of intimidation and race-baiting.
“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,” Governor Ed Rendell said.
Mr Rendell, a Democrat, and Republican US Senator Arlen Specter were among the politicians who called on the FBI to tell the public what it knows about the eavesdropping equipment. That list also included Mr Katz, who called the discovery “breathtakingly shocking”.
The FBI made no such public disclosure, and it was unclear what federal prosecutors revealed to Street about the investigation in the two days since the bugs were discovered.
Three federal law enforcement officials, who spoke on condition of anonymity, acknowledged that the FBI was responsible for the bugs, but refused to provide any details about the nature of the probe.
Street said one of his advisers had been told by the US attorney’s office that the mayor was not the target of an investigation.
“I now feel vindicated because obviously the US attorney has said that I’m not part of any investigation. I feel good about that,” Mr Street said yesterday morning. His comment went further than the statement he issued Wednesday night, in which he said he had never believed he was the “target” of an investigation.
The US attorney’s office in Philadelphia did not acknowledge responsibility for the bugs but said it had been in touch with Mr Street.
“We have stated very clearly to both Mayor Street and his attorney the mayor’s status in this matter,” spokesman Richard Manieri said on Wednesday night.
He would not elaborate on what federal prosecutors told Street.
FBI spokeswoman Linda Vizi declined to comment on the devices, other than to say they were not connected to campaign espionage. The devices were found on Tuesday by police conducting a routine sweep of Mr Street’s City Hall office suite.
Mr Street’s campaign suggested the bugging was instigated by Republicans.
“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,” said Frank Keel, the Street campaign spokesman.
Mr 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.”
US Attorney Patrick Meehan, the top federal prosecutor in Philadelphia, denied politics plays any role in prosecutors’ decisions. Election day is November 4. “The US 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,” he said in a statement.
Philadelphia Police Commissioner Sylvester Johnson said the security sweeps of the mayor’s office have been going on for decades. Police said a similar sweep done in June found nothing suspicious.
An aide to Mr Street 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. Mr Street beat Mr 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, which has been marked by ugly words and an act of violence.