UPDATE | Navy finds no sign of shooting at center; lock down lifted

SAN DIEGO (AP) — Authorities found no gunman or signs of a shooting on today after receiving a report from a Department of Defense employee that shots had been heard at one of the nation's largest Naval medical facilities.

The report of a shooting grabbed attention across the country and led to the lockdown of Naval Medical Center San Diego in Balboa Park, near the San Diego Zoo, and three nearby schools.

Authorities lifted the lock down on the facility this afternoon.

Fears were heightened when the medical center posted on its Facebook page that, "An active shooter has just been reported in building #26 at Naval Medical Center San Diego. All occupants are advised to run, hide or fight."

The unidentified Department of Defense employee reported hearing three gunshots just before 8 a.m. on the sprawling 78-acre campus, where Building 26 houses administrative offices, a gymnasium and dormitories for combat-wounded veterans in long-term care. As many as 800 people work in the building.

All nonemergency personnel were asked to stay away from the area and traffic backed up around the facility during the morning rush hour.

Military personnel searched the structure for about two hours before saying there were no initial signs of a shooting.

The base remained on lock down hours later as military police went room to room and led personnel out of the building.