Local authorities in San Diego are investigating reports of an "active shooter" at a San Diego military hospital. Police have failed to find any evidence that a shooting occurred.
Navy spokesman Jon Nylander told AFP news agency on Tuesday that a single witness had reported hearing three shots in the basement of Navy Medical Center at around 8:00 a.m. local time (1500 UTC).
The medical center wrote on its Facebook page shortly after that "an active shooter" had been reported in Building 26 of the hospital.
"All occupants are advised to run, hide or fight," the statement added.
Local news station CBS 8 also reported that police had confirmed shots were fired outside Building 26 on the hospital's third floor.
San Diego, the southernmost city on the California coast, has a wide military infrastructure and is a major port for the US Navy.
The US has seen several deadly shootings at military installations in recent years. In November 2009, 13 people died and more than 30 were wounded after US Army psychiatrist Major Nidal Hasan opened fire at Fort Hood military base in Texas.
In September 2013, Aaron Alexis killed 12 people and wounded eight others at the Washington Navy Yard, just two miles (three kilometers) from the US Capitol building.