The U.S. government is expressing doubts about a threat posted on the Internet which warns officials in seven U.S. cities about a dirty bomb attack on professional football stadiums in the coming days.
The U.S. Department of Homeland Security said Wednesday the threat was being viewed "with strong skepticism," but that an alert was being issued "out of an abundance of caution."
Authorities say the threat was posted on an Internet web site and mentions National Football League, or NFL, stadiums in New York, Miami, Atlanta, Seattle, Houston, Oakland and Cleveland.
Officials, however, say people are strongly encouraged to continue to go about their plans, including attending events that involve large public gatherings such as football games.
Some information for this report was provided by AP and Reuters.