A US military complex in Washington DC has been given the all clear after reports that a gunman was on the site.
Hundreds of police officers flooded the US Navy Yard, which was evacuated after the false alarm on Thursday morning.
But after scouring the site, officials said police had found no sign of a shooting, made no arrests and found no weapons.
The sprawling site in the southeast part of the US capital was the scene of a mass shooting two years ago.
Aaron Alexis, a former contract worker, killed 12 people and wounded three others in September 2013.
The BBC’s Tara Neil at the scene said officers had focused their attention on building 197, the site of the 2013 shootings.
The building serves as the headquarters for the Naval Sea Systems Command, which builds and maintains ships and submarines for the Navy.
Washington Navy Yard, which is the US Navy’s oldest shore installation, was first opened in the early 19th Century, according to the Navy.