Pelosi, who along with Gov. Ed Rendell and other lawmakers marched with Street in the city's Columbus Day parade, questioned the timing of the FBI investigation. Listening devices were found in Street's office on Tuesday, just a month before the Nov. 4 election.
"The probe raises serious questions about the timing of it," said Pelosi, D-Calif. "Also that they would announce that it's not campaign-related raises even more questions about whether it is campaign-related."
Many voters said the investigation surrounding Street has not affected their plans for next month's election. Supporters of both Street and Republican challenger Sam Katz said they made up their minds long ago.
Since the listening devices were found in City Hall, Street has said repeatedly that federal prosecutors have told him he is not a target in a criminal investigation.
The FBI has said the bugs are not connected to the campaign.
A federal official, speaking on the condition of anonymity, told The Associated Press on Friday that Street is a "subject" in an investigation. The legal term is used to describe a person whose conduct is believed to be within the scope of a criminal probe, although they themselves may not be suspected of breaking the law.
Katz denied again Sunday that he had anything to do with the investigation.
At Bright Hope Baptist Church, the Rev. William H. Gray III, a former congressman and retiring president of the United Negro College Fund, gave a sermon in which he beseeched the FBI to be more specific about its investigation.
"Don't leave a cloud hanging over our city in this election process," said Gray, who met privately with Street afterward. "You need to be clear and say just what it is and who it is."
Lorraine Williams, a Democrat who attended the sermon, said her support for Street would not change.
"Either party, it's always something that's going to happen just before the election," said Williams.
Many Katz supporters said news of the bugs also hasn't affected their thoughts.
"I'm at the same place I was before," said Pamela Boice, a Republican.
Jack McLaughlin, a Democrat, said he had decided to vote against his party's candidate long before word of any probe.
"I never liked Street," he said. "I never did. I never will."
By Patrick Walters