BETHESDA, Md. (AP) — Security officers found "no indication" of an active shooter after reports from Walter Reed National Military Medical Center outside Washington, officials said Tuesday.

Naval Support Activity Bethesda tweeted at 2:15 p.m. that an active shooter had been reported in the basement of a building at the Maryland base.

NSAB public affairs officer Jeremy Brooks told AP by phone that "right now there is no indication that there is any active shooter, but we won’t know 100 percent until the buildings have been successfully cleared."

Brooks said "we’ve stopped all traffic coming in or out." He had no timeline for when clearance activities would be completed.

U.S. Rep. Dutch Ruppersberger of Maryland said in the tweet that he and about 40 other people were in a conference room at the hospital.

The Montgomery County Police Department was called to the scene just after 2:20 p.m., Officer Rick Goodale said.

"We have officers out there, but as of yet we haven’t been able to confirm this report," he said.

Walter Reed is the nation’s largest military hospital and according to its website, is among the first stops in the continental United States for troops wounded in combat.

NSAB oversees operational support for its major tenants at the base, including Walter Reed.