Updated 3:25 EST
BETHESDA, Maryland -- Police say there is no evidence of gunshots and no injuries reported at a major military hospital outside the U.S. capital after someone made an emergency call to say they heard a single shot fired there.
Police have searched a 20-story tower at the Walter Reed National Military Medical Center outside Washington after receiving the call from the tower Monday morning.
Police spokeswoman Natasha Plotnikov says police will now bring in dogs to search the building for explosives. She says people are still sheltering in place.
The U.S. Navy's website warns that the campus is on lockdown 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.
Montgomery County police spokeswoman Natasha Plotnikov says a 911 caller reported hearing one shot inside Building 1, the original hospital on the campus in Bethesda, on Monday morning. She says police are on the scene checking the report.
Local television coverage shows police cars parked by the building and people walking away from the building.
Police tweeted that they have not confirmed the report of a shot, but they are sending additional officers.
Walter Reed officials could not immediately be reached.