After a six-hour lockdown, law enforcement agents found no evidence that an armed man had gotten inside No suspects have been found and hospital staff were still sheltering in place Thursday morning at San Diego's largest military medical facility. No suspects were found after the false alarm, the second at following multiple reports of an armed man on base, according to a Navy spokeswoman. It is the second lockdown at Naval Medical Center San Diego in two months, after a shots fired report in January triggered a full-scale law enforcement response that turned out to be a false alarm.

Law enforcement teams continue to combed buildings looking for an armed gunman, a Navy spokeswoman said, while an earlier report of a bullet found on the ground is unconfirmed. 

"There's been no person found that matches the description of what the caller said they saw," Lt. j.g. Madison McSweeney, a spokeswoman for Navy Region Southwest, told Navy Times.

An anonymous phone call Thursday morning offered a description of a man carrying an unspecified firearm, McSweeney said.

The base set a shelter-in-place order at 7:28 a.m. local time, which requires patients and employees to stay in their rooms or offices until security can sweep the premises and begin evacuations.

NMCSD issued a "code white" — a hospital term for a violent or behavior situation —  via its official Facebook page.

Hospital employees and personnel were also told not to come into work and traffic was diverted from the base. The lockdown was lifted around 5 p.m. local time.

It's the second report of a possible shooter on that base this year, after a January investigation into shots fired turned out to be a false alarm.

In the January false alarmthat situation, on-base personnel were encouraged via Facebook and inter-office message to "run, hide or fight" if circumstances called for it.