Federal agents raided City Hall in New Jersey's capital on Thursday, one day after they swarmed the home of the city's mayor, his brother and a campaign supporter.
"The FBI is executing search warrants at various offices at Trenton City Hall, pursuant to an ongoing investigation," said FBI spokeswoman Barbara Woodruff.
It was not immediately clear why the raids were conducted and authorities declined to elaborate.
Mayor Tony Mack, 46, responded to the Wednesday raids by saying he had "not violated the public trust in any way, nor have I violated any of my public duties."
He could not be immediately reached Thursday for comment.
Mack, a Democrat who began his term in July 2010, has been beleaguered by questions over public finance and accusations of cronyism.
Last May, his deputy mayor, Paul Sigmund IV, was arrested and charged with heroin possession and assaulting a police officer, which led to his prompt resignation.
Wednesday's raids also included the homes of Mack's brother, businessman Ralphiel Mack, and Joseph Giorgianni, a convicted sex offender.