He was indicted Thursday on charges that include money laundering, conspiracy and bribery.
The corruption allegations involve his time as Ohio's deputy treasurer.
Mayor Rahm Emanuel says he has no reason to believe there was any wrongdoing during Ahmad's two-year tenure here in the Finance Department.
Ahmad is Ohio's former state deputy treasurer. Federal prosecutors in Ohio charged him Thursday for crimes they say occurred between 2009 and 2011.
The 38-year-old was named to the Chicago post in May 2011, but he resigned from his job last month, saying he was going to work in the private sector.
Statement for mayor's spokesperson Sarah Hamilton:
"The Mayor has a record of zero tolerance for the kind of criminal violations and abuse of the public trust that are alleged in this indictment. We had no knowledge of the investigation until today's news reports, and it appears to be focused on alleged activities when Ahmad served the State of Ohio. We have no reason to believe and have no knowledge of any such wrongdoing during his tenure in Chicago. But we will take any action that is needed - including conducting a review of Finance Department activities over the last two years - to ensure that Chicago taxpayers are protected."
The Associated Press contributed to this report.