"An active shooter has just been been reported in building #26 at Naval Medical Center San Diego," the message stated. "All occupants are advised to run, hide or fight."
Local media reported that at least three shots have been fired in the center.
The hospital urged all non-emergency personnel to stay away from the facility.
Over the past year, the United States has seen a growing number of mass shooting incidents. In December, a radicalized couple shot and killed 14 people at the Inland Regional Center in in the southern California city of San Bernardino.
According to some latest reports no evidence of shooting had occurred.
Navy officials say report of gunshots at San Diego base came from 1 person. Not confirmed.— Chris PIlz (@chrispilz) 26 января 2016