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SAN DIEGO — 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.

The incident is being treated as an active shooter situation, center spokesman Mike Alvarez said.

There were no immediate reports of anyone injured, military officials speaking on condition of anonymity said. Further information about the gunfire wasn’t immediately available.

Military and local police were going through the building. The center, on its Facebook page, said that “all occupants are advised to run, hide or fight.”

“All non-emergency response personnel are asked to stay away from the compound,” the post reads.

Investigators were interviewing the person who made the report about shots being fired, a U.S. military official said.

Naval Medical Center San Diego bills itself as the largest military healthcare system in the western United States. Situated on 78 acres surrounded by San Diego’s Balboa Park, the center has a 272-bed hospital, eight clinics for active duty personnel and nine primary care sites for their family members.

The center had more than 1.2 million outpatient visits in 2014, admitting more than 19,000 patients that year. The hospital offers a comprehensive array of medical services, including births.

Video captured by CNN affiliate KUSI showed people walking calmly from the area Tuesday morning.

Law enforcement took up positions nearby, directing pedestrians and cars away from the building in question.

Nearby restaurant Casa 1915 is keeping its doors closed as a precaution. The bistro was set to open at 10 a.m. PT, but manager Keith Puryear told CNN he decided to keep the business closed until the situation at the medical center ends.

Police haven’t asked him to do that, it’s a decision he made on his own.

“We’re not terribly concerned at the moment,” he said, “but we’re exercising caution.”

The child care facilities at the medical center “are currently secured,” Naval Base San Diego said around 9 a.m. (noon ET) on its Facebook page. “All children are accounted for and safe. The entire complex is secured.”

A middle school and two high schools in the vicinity were locked down as a precaution, the San Diego Unified School District said.

Developing story — more to come

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