The FBI said on Thursday that they questioned an unidentified Milwaukee individual over the posting of a terrorism threat against National Football League stadiums. ``The U.S. government still believes this threat is non- credible,'' Richard Ruminski, special agent in charge of the FBI's office in Milwaukee, said in a statement. The U.S. Homeland Security Department yesterday, citing an ``abundance of caution,'' warned the NFL about the threat, which claimed an al-Qaeda operative had smuggled deadly radioactive materials into the U.S. from Mexico.