Union Station in Washington was evacuated around 5:45 p.m. Wednesday, but Metropolitan Police have not confirmed a reason for clearing the station.
The transportation hub was reopened shortly after 6 p.m. WUSA reported the closure had been in response to a fire alarm going off.
The station is a few blocks north of the U.S. Capitol. The historic station is one of the busiest transportation hubs in the nation. It houses a shopping mall, large food court and Metro, Amtrak and commuter train service and various bus stops.
It's the second time in a month the station has been evacuated. Thousands of commuters have been pushed outside of the building and trains have been canceled.