MANHATTAN - Some New Yorkers called for the impeachment of Mayor Bill de Blasio Sunday amid a federal investigation.

Community advocates Tony Herbert and John Rodriguez joined residents in a rally outside City Hall in Manhattan to call on the mayor to step down or have him forced from office.

"He cannot represent our city under a criminal investigation," Herbert says. "That is a conflict of interest for us and it compromises our integrity, so our belief is that he needs to step down."

The FBI is investigating the mayor over campaign fundraising back in 2012 as part of a widening probe into the NYPD.

So far, nine police officials, including four deputy chiefs, have been transferred or stripped of their guns and badges as internal affairs detectives and FBI agents examine whether officers accepted gifts and trips from businessmen in exchange for police escorts, special parking privileges and other favors.

Subpoenas also have sought records related to hundreds of thousands of dollars in donations solicited by the mayor's campaign that were rerouted to upstate Democrats running for the state Senate, The New York Times has reported.

Separately, federal agents operated a wiretap that captured the conversations of two businessmen, Jona Rechnitz and Jeremy Reichberg, who were friends with two top police officials and served on de Blasio's inaugural committee in 2013 and contributed to his campaign, two law enforcement officials said.

Investigators reportedly want to know whether they have been offered any official favors in exchange for donations.

De Blasio, a Democrat, has not been accused of any specific wrongdoing and his campaign organization has said it operated within the laws.

The mayor's press secretary said in a statement, "We are confident that all of our efforts were appropriate and in accordance with the law at all times."

AP wire services contributed to this report.