Bethesda - Police say there is no evidence of gunshots and no injuries reported at a major military hospital outside the US capital after someone made an emergency call to say they heard a single shot fired there.
Police have searched a 20-storey tower at the Walter Reed National Military Medical Center outside Washington after receiving the call from the tower on Monday morning.
Police spokesperson Natasha Plotnikov says police will now bring in dogs to search the building for explosives. She says people are still sheltering in place.
The US Navy's website warns that the campus is on lock-down after a report of an active shooter.
Roads around the facility were closed for hours but are now open. Police and the Navy tweeted that all patient care at the facility has been suspended for the day.