Investigators found "absolutely nothing" to substantiate a report gunshots were fired at a California naval hospital, the US navy says.
A witness reported three gunshots at the Naval Medical Center in San Diego prompting officials there to urge people to stay away as police responded.
However, a US Navy spokesman Captain Curt Jones said military and local police were still going through the building at Naval Medical Center in San Diego, and it would take a long time to finish their search.
They are also interviewing the person who made the report about shots being fired, CNN reported.
The San Diego centre serves wounded soldiers and also has primary care sites for soldiers' family members.
The witness had reported in the basement of the centre's Building 26, a combination gym and barracks building, about 8am local time.
Earlier, a spokesman for the hospital, Mike Alvarez, said the incident was being treated as if it was an active shooter situation.
The centre, on its Facebook page, also relayed the report and said that "all occupants are advised to run, hide or fight."
Comments on the Facebook page said that that though shots had been fired, the military and San Diego police have the situation under control.
An updated post told all staff to remain clear of the centre while the investigation continued.
There have been no reports of injuries.
Three schools in the area were locked down as a precaution.
With over 6,500 personnel, the hospital also serves as a training facility for nursing schools in the area.
- RNZ / BBC / CNN