All-Clear at Top U.S. Military Hospital after Gunshot Scare

Authorities gave the all-clear at a U.S. military hospital complex outside Washington on Monday after reports of a gunshot prompted a lockdown -- the second such false alarm in a week in the capital area.

Staff at the sprawling Walter Reed National Medical Center were ordered to shelter in place as police with sniffer dogs combed its 20-story main building, but investigators found no sign of any shots fired.

"#USNavy confirms all clear at #WalterReed / Naval Support Activity Bethesda. Police found no evidence of gunshot. No injuries," the Navy said on Twitter.

"There is no evidence or any indication of a firearm being discharged," Montgomery County Police spokesman Captain Paul Starks said.

Officers meanwhile interviewed the individual who made the initial call at 10:48 am (1448 GMT), Starks told reporters at the scene.

"They heard some noise that they thought could have been shots," he said, and police responded in force amid fears there could be an active shooter on the premises.

Staff took cover as a "code white" lockdown was declared at the facility in Bethesda, Maryland, where 7,000 people are employed and security is described as tight.

One member of staff described colleagues and patients hiding in a bathroom with the lights off, amid shouts in the hallways for people to stay put.

Live video from local TV news showed hospital staff -- some in white smocks -- exiting the main building with their hands in the air.

The lockdown at the nation's top military hospital followed a weekend of heightened security in the United States for the Independence Day holiday.

It also came days after a similar false alarm about gunfire prompted a lockdown at the Washington Navy Yard -- scene of a mass shooting in 2013 in which a lone gunman killed 12 people.

Walter Reed serves patients ranging from Iraq war veterans to President Barack Obama.