Maryland police are responding to a report of a shot fired at the Walter Reed Medical Center campus in Bethesda. Naval support activity in Bethesda is currently in lockdown mode though there has been no official confirmation of a shooting.

Through a series of tweets, Montgomery County Police Capt. Paul Starks said officers were asked to assist federal partners at Walter Reed after reports of a single gunshot.

A 911 caller reported hearing one shot inside Building 1, the original hospital on the 243-acre campus in Bethesda, on Monday morning.

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 “out of an abundance of caution.”

Walter Reed officials could not immediately be reached.

The Associated Press contributed to this report.