(CNN) --The FBI planted an electronic bugging device in Philadelphia Mayor John Street's office, a senior federal government source and two law enforcement sources told CNN Wednesday.
But the FBI disputed the report.
"We have not confirmed that at all," said FBI Special Agent Linda Vizi. "When the bug was found, we were made aware of it, and we will proceed from there."
The sources would not say whether Street was the target of a public corruption investigation going on in Philadelphia, the sources told CNN.
Rich Manieri, a spokesman for U.S. Attorney Patrick Meehan, said "Justice Department policy is to neither confirm or deny an investigation."
Street said he doesn't know why the device was placed in his office or who put it there. It was found Tuesday during a routine security sweep by Philadelphia police, and the FBI was called in to investigate.
Street told reporters Tuesday he was not involved in any activities that he knew to be under investigation.
"I have done nothing wrong," Street said.
Street, a Democrat, is campaigning for re-election November 4 in a close race against Republican Sam Katz, whom he beat four years ago in a close race.
Street said bug's "timing is very suspicious" and that it was possibly politically motivated.
The mayor's rival was cautious in his remarks about the device and said any "innuendo" about Republicans being to blame was unfair.
Katz asked for the situation "to be clarified as quickly as possible" and said it was important for the city to know sooner rather than later why the bug was planted.
Pennsylvania Gov. Ed Rendell said if the mayor was not the target of an investigation, "then the FBI owes that explanation not only to the mayor, but to the people of Philadelphia."
Police Inspector Bill Colarulo told CNN the sweeps are done periodically, and the last one had been performed three or four months ago. He said the police commissioner notified the FBI, which now has the evidence.
The bug's discovery prompted Sen. Arlen Specter, R-Pennsylvania, a senior member of the Judiciary Committee, to call on the Justice Department to release any information it has about the bugging.
CNN's Kelli Arena, Deborah Feyerick, Terry Frieden and Phil Hirschkorn contributed to this report.
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