Chicago Mayor Richard Daley underwent questioning by federal authorities in 2008 as part of their investigation into the relationship between a real estate developer and a corrupt alderman, published reports say.
The revelation, published by the Chicago Tribune and the Chicago Sun-Times, comes a day after Daley was released from the subpoena in the bribery case of Chicago developer Calvin Boender.
There is no suggestion that Daley violated any law or was under investigation himself.
Boender is accused of bribing then-Ald. Isaac "Ike" Carothers with $40,000 in home improvements, meals and tickets to a White Sox playoff game to win a zoning change for the Galewood Yards development on the city's West Side.
Boender pleaded not guilty to four counts of mail fraud, two counts of obstruction of justice, two misdemeanor counts of violating federal campaign finance laws and one count of paying a bribe.
Carothers has pleaded guilty in the case, is cooperating with prosecutors and has resigned from the City Council.
