"We received word that our base emergency personnel responded to reports of gun shots," staff sergeant Nicole Leidholm, a spokeswoman at Travis Air Force Base, told AFP.
"However, no shooter was found. The base is no longer on lockdown."
Leidholm said the alarm was sounded at approximately 3:15 PM (local time) yesterday, prompting officials to urge all personnel, dependents and retirees at the sprawling facility to seek shelter or avoid the base.