Milwaukee (AP) -- It's a hoax.
The government says the threats about "dirty bomb" attacks on NFL stadiums this weekend turned out to be some kind of internet prank.
The FBI and Department of Homeland Security say they reached the conclusion after agents questioned a 20-year-old Milwaukee man. Agents say the man has been released, but authorities still want to talk to him to figure out who posted the threats.
An FBI spokeswoman in Milwaukee says it's not clear what his involvement was or if he'll be charged. Another bureau official says the man didn't seem to have any connection to terrorist groups.
The threats about radioactive bombs were posted on a web site a week ago. Although the NFL and the public were told about them, officials said from the start they were highly skeptical they were real.