Montgomery County Police and military security officers Monday were investigating an unconfirmed report of a gunshot heard on the campus of the Walter Reed National Military Medical Center in Bethesda.

The campus was in lockdown.

County police were on the scene and working with federal partners, but have not confirmed the incident, on the second floor of building 1.

[ Watch live: Report of gunfire at Walter Reed ]

Personnel are said to be sheltering in place. Calls to the medical center were being referred to the public affairs office, where no one answered the phone.

A local law enforcement officials said no shooter or victims had been located as of about 11:45 a.m.

The medical center is at 8901 Rockville Pike, where traffic was said to be badly snarled.

The campus covers 243 acres, has 274 beds and a staff of 7,000.

Shortly after noon, the U.S. Navy tweeted that security officers were searching buildings, and there was no confirmation of an incident.

The Navy added in a statement:

“Naval Support Activity Bethesda is currently in lockdown and all base personnel are sheltering in place as a result of unconfirmed reports of an active shooter. DOD Security Force, NIH Police Force and County EMS and Medics have responded and are searching the area. More information to follow.”