Authorities have found no evidence of a shooting at a key US Navy site in Washington, no one has been arrested, and no weapons have been found after a report of gunfire.
An official said authorities received an alert about a potential shooter at the Washington Navy Yard installation, which triggered a large response in keeping with protocols established after a gunman killed 12 workers in a 2013 massacre.
No injuries have been reported.
Navy security saw surveillance video of two people jumping the fence in the vicinity of the building a couple of minutes before the first report of gunfire, a federal official had said earlier.
Security found no one inside the building, the official said.
A heavy police and fire department presence began blocks away from the Navy Yard, with roads blocked and a helicopter hovering overhead.
Gates to the Navy Yard were closed, and all people were being advised to shelter in place, said Chatney Auger, spokeswoman for Naval District Washington.
Thousands would be at the base at the time of the reports, Navy public affairs officer Chris Johnson told reporters outside the facility.
In September 2013, military contractor Aaron Alexis killed 12 civilian workers at the Navy Yard’s Building 197 before he was fatally shot by police. The building has since been renamed the Humphreys Building. It reopened this year.
The Navy Yard is the oldest naval installation in the United States.