JUST IN: Police evacuate U.S. Capitol, Visitors' Center

Police have evacuated the U.S. Capitol and the visitors' center.

Capitol police provided no explanation for the move, simply saying it was an emergency. In a message to congressional offices, police said, "an evacuation has been ordered for U.S. Capitol Visitor Center due to an audible alarm. Remain calm and move in a safe manner to the exits."

Hundreds of tourists were forced out of the building onto the East Lawn between the Capitol and the Library of Congress.

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