Federal authorities Friday charged a Wisconsin man with making a hoax threat that said seven football stadiums across the nation would be targeted by terrorists with radiological "dirty bombs" this weekend.
The U.S. Attorney's Office in Newark did not immediately identify the man but said in a news release announcing the charge that he would be in court in Milwaukee later Friday.
One of the stadiums allegedly targeted was Giants Stadium in East Rutherford, New Jersey.
The FBI determined the threats were a hoax on Thursday.
A joint statement from the FBI and Homeland Security Department said fans "should be reassured of their security as they continue to attend sporting events this weekend."
An FBI official in Washington, who spoke on condition of anonymity because the case is still under investigation, told The Associated Press that a Milwaukee man acknowledged posting the phony stadium threat as part of a "writing duel" with a man from the Brownsville, Texas, area to see who could post the scariest threat.
The Texas man corroborated the story during questioning Thursday by FBI agents, the official said.
The threat, dated Oct. 12, appeared on the Web site "The Friend Society," which links to various online forums and off-color cartoons. Its author, identified in the message as "javness," said trucks would deliver radiological bombs Sunday to stadiums in Miami, Atlanta, Seattle, Houston, Cleveland, Oakland, California, and the New York City area, and that Osama bin Laden would claim responsibility.
The agency alerted authorities Wednesday in the cities mentioned, as well as the National Football League and the National Collegiate Athletic Association. But the FBI and Homeland Security said there was no intelligence indicating such an attack might be imminent.
Milwaukee police contacted the FBI about the 20-year-old man Wednesday night.
The man questioned did not appear to have any ties to terrorist groups, according to the official who spoke on condition of anonymity.
NFL spokesman Greg Aiello said stadiums are well protected through "comprehensive security procedures" that include bag searches and pat-downs.
Associated Press writers Lara Jakes Jordan and Hope Yen in Washington and Emily Fredrix in Milwaukee contributed to this report.