Authorities in Washington said Thursday they have found no evidence of a shooting at the U.S. Navy Yard in Washington, hours after locking down the country's oldest naval installation in a security alert as they searched for a possible shooter.
No arrests had been made, no weapons were discovered, and no injuries were reported at the Navy Yard, which is an administrative center for the U.S. Navy, officials said Thursday morning.
Dozens of police vehicles, sirens blaring, converged on the facility just blocks from the U.S. Capitol, after police said they received an emergency call about a possible shooting about 7:30 a.m. EDT (1130 GMT).
But after more than two hours of searching, police signaled the area was "all clear."
By midmorning, some of the police that swarmed the area around the Navy complex were beginning to disperse.
Heavily armed police searched room by room in the same Navy Yard building where in September 2013 a military contractor, Aaron Alexis, shot and killed 12 civilian workers before he was shot dead by police.
About 6 kilometers (4 miles) away, security was tightened outside the White House, with officials closing the pedestrian mall that runs along Pennsylvania Avenue and the adjoining Lafayette Square.
Authorities ordered civilian and military members arriving early to work Thursday to stay out of the building while the incident was investigated. Televised accounts from the scene showed police wearing bullet-proof vests heading into the complex.
The incident is unfolding two days before the country's July 4 Independence Day celebration.
Earlier this week, the Department of Homeland Security and the Federal Bureau of Investigation issued an alert calling for local authorities and the public to remain vigilant for possible threats during the holiday weekend.
VOA's Victoria Macchi is on the scene.
Some material for this report came from AP, AFP and Reuters.