A spokesman for the Economic Financial Crimes Commission told The Associated Press on Thursday that authorities questioned Adamu for eight hours on Wednesday in Nigeria's capital Lagos.
Femi Babafemi says Adamu was asked about an alleged $800,000 bribe for World Cup bids and other allegations dating to before he was a FIFA executive.
He said "investigations are still in process." Adamu sought a court order a week ago to prevent local authorities from investigating him over the FIFA scandal, saying they lacked authority to do so.
He returned to Nigeria on Tuesday for the first time since his suspension.