WASHINGTON - The U.S. Capitol was briefly evacuated Saturday afternoon when a small aircraft entered restricted airspace, authorities said.
The evacuation was ordered after authorities were unable to immediately contact the pilot, U.S. Capitol Police said.
NORAD says two F-16 fighter jets intercepted the plane around 1:30 p.m. after it entered restricted airspace and was out of communication with air traffic control.
The jets escorted the plane to the airport in Mount Airy, North Carolina, where the pilot was met by members of law enforcement.
Staff and visitors later were allowed back inside the Capitol.
Also evacuated during the scare was the Library of Congress and the U.S. Supreme Court buildings, the Metropolitan Police said.
Federal Aviation Administration officials told CNN there will be an investigation into why the pilot entered the restricted airspace without authorization.
The incident prompted authorities to institute an AIRCON RED -- air condition red -- alert, police told CNN. The alert is triggered when an aircraft enters restricted airspace in Washington without authorization.
Visitors to Washington got unexpected excitement.
"We were touring around in the, one of the rooms in the Capitol," said Victoria Chandler. "And the tour guide all of a sudden got very frantic and started telling us to evacuate the building and go down the steps.
"I grabbed two of the youngest girls and my mother got me and we started running down the stairs. We got outside and a man told us to run as far as we could because it was not a drill."
Richard Chapin was also in the Capitol.
"We just got in there, like I said, we were excited to see it," he said. "Now we've got a story to tell. We were evacuated out of the Capitol building."
It's not the first time such an alert has been issued.
The Capitol was briefly cleared and the White House was temporarily locked down when a single-engine plane wandered into restricted airspace in April 2009.
It was also evacuated in January 2011 when a commercial airliner accidentally entered restricted airspace.