NEW YORK, NY - SEPTEMBER 09: Transportation Security Administration officers screen baggage as the Amtrak Police and K9 dogs keep a careful eye on passengers at Penn Station September 9, 2011 in New ... more 
NEW YORK, NY - SEPTEMBER 09: Transportation Security Administration officers screen baggage as the Amtrak Police and K9 dogs keep a careful eye on passengers at Penn Station September 9, 2011 in New York City. U.S. government officials said yesterday evening that there is a "specific, credible but unconfirmed threat" to the U.S. homeland as the 9/11 anniversary approaches and that New York and Washington were specifically mentioned as possible targets. (Photo by Chip Somodevilla/Getty Images) less 
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Getty Images | Photo By Chip Somodevilla / Getty Images
Fri, Sep 9, 2011 1:55 PM EDT