(CNN)Gunfire was reported Tuesday morning at the Naval Medical Center San Diego, the Navy said, prompting the center to urge people to stay away as police responded.

One witness reported hearing three gunshots in the basement of the center's Building 26, a combination gym and barracks building, at about 8 a.m. PT (11 a.m. ET), Navy spokesman Kevin Dixon said.

A spokesman for the center, Mike Alvarez, said the incident is being treated as an active shooter situation. Further information about the gunfire wasn't immediately available.

An active shooter was reported at a building at the Naval Medical Center in San Diego, prompting a lockdown, authorities reported Tuesday.

The medical center posted on its Facebook page shortly after 8 a.m. local time that an active shooter had been reported in a building at the facility.

“All occupants are advised to run, hide or fight,” the message stated.

“All occupants are advised to run, hide or fight,” the message stated.

No casualities, no evidence of gunshots and and no injured personnel have been found in a sweep of the Naval Medical Center San Diego, authorities said Tuesday.

Reports of a possible active shooter around 8:22 a.m. caused the medical center to issue an alert telling hospital occupants to “run, hide or fight.”

“Apparently someone said they heard three shots in the basement of Building 26. Maybe they did or not is not the point; that’s what they reported, so that’s why we responded accordingly,” said Jon Nylander, Navy spokesman. “We haven’t gotten any reports of any injuries.”

beaurrr wrote:

“All occupants are advised to run, hide or fight,” the message stated.

What other options would there be, exactly?

inomaha wrote:Another option is arm yourself and fire blindly at whatever moves.

That's not a good option, but ranks just ahead of asking them to take a number and fill out the appropriate paperwork before being called.

inomaha wrote:Another option is arm yourself and fire blindly at whatever moves.

That's not a good option, but ranks just ahead of asking them to take a number and fill out the appropriate paperwork before being called.

beaurrr wrote:

“All occupants are advised to run, hide or fight,” the message stated.

What other options would there be, exactly?

beaurrr wrote:

“All occupants are advised to run, hide or fight,” the message stated.

What other options would there be, exactly?