They say at approximately 7 p.m., Travis AFB first responders and Fairfield emergency officials responded to an incident where a car gained unauthorized access to the base through the main gate entrance. The car crashed shortly after entering the base and became engulfed in flames.
A U.S. officials told ABC News that it appears there were propane tanks inside that vehicle.
Security officials responded immediately, and the base's Explosive Ordinance Disposal team, Office of Special Investigations and other responders were on the scene.
The driver of the vehicle was pronounced dead at the scene. There were no additional fatalities or injuries, officials say.
The identity of the driver has not been released at this time.
U.S. officials are looking at terrorism or some sort of suicide event as a possible motive, but the investigation is in its early stages.
Air Force Office of Special Investigation and the FBI are currently investigating and there are no current known threats to the base or community.
The main gate has reopened and all other facilities are operating as normal.