Internet threats of "dirty bomb" attacks at NFL stadiums this weekend were a hoax, the FBI and Department of Homeland Security said on Thursday.
The FBI made the announcement after agents questioned a 20-year-old Milwaukee man in an effort to determine who made the threats against the pro American football league games, which were posted on a Web site last week.
"The investigation has determined that this is a hoax. The public should be reassured of their security as they continue to attend sporting events this weekend," said the agencies' joint statement.
The FBI did not immediately say whether charges will be filed against the man. Milwaukee police contacted the FBI about the man on Wednesday night.
"From the information we have, we believe he was involved to some extent, but we don't know at what level," said FBI agent Douglas Porrini. He added: "That person was released, but we're not saying that he won't be charged."
The threat, dated Oct. 12, appeared on a Web site, The Friend Society, that links to various online forums and off-color cartoons. Its author, identified in the message as "javness," said trucks would deliver radiological bombs on Sunday to stadiums in New York, Miami, Atlanta, Seattle, Houston, Cleveland and Oakland, California, and that Osama bin Laden would claim responsibility.
The Homeland Security Department alerted authorities in the cities mentioned. But the FBI and Homeland Security said there was no intelligence indicating such an attack might be imminent.