Emergency crews immediately responded to the reports, but no shooter was found, officials said. The base is no longer on lockdown, Travis Air Force base's Public Affairs office told TIME.
The base, located in Solano County, California, received notice at approximately 3:15 P.M. pacific time that possible shots had been fired, and posted about the threat on its Twitter and Facebook pages.
The public was asked to stay away from the base, and everyone remaining on the base was asked to shelter in place.
"We take every security incident seriously," Travis Air Force Base tweeted after announcing it had lifted the lockdown. "Thank you for your patience."