FBI and Air Force jointly investigating deadly vehicle crash at Travis Air Force Base The driver was pronounced dead at the scene.

The FBI and the Air Force's Office of Special Investigations are jointly looking into why a vehicle crashed shortly afterward gaining access to Travis Air Force Base in California Wednesday night, the Air Force confirmed.

Investigators are trying to determine what the possible motive may have been for the incident that left the driver dead after the vehicle was engulfed in flames. A U.S. official said it appears that there were propane tanks inside the vehicle.

The vehicle gained access to the main gate at Travis, crashing shortly afterward and catching fire, the base said in a statement.

"The driver of the vehicle was pronounced dead at the scene," the statement read. "There were no additional injuries."

The incident began when guards at the main checkpoint to enter Travis AFB saw a vehicle moving slowly towards the checkpoint, said a U.S. official.

When they motioned for the vehicle to stop the car ignited and ended up rolling onto a median towards the opposite lane of traffic, the official said.

It appeared there were propane tanks inside the vehicle, the U.S. official said.

There were no shots fired during the incident, a defense official told ABC News. The official added that the driver of the vehicle was a civilian, not a service member.

The U.S. official said investigators are looking at a broad range of potential motives, including whether the driver was mentally unstable, or whether it could be possible terrorism or a suicide.

The official said investigators are in the initial stages of the investigation and there are more questions than answers about this incident.

The Air Force said there are no current known threats to Travis or its community. The main gate has reopened, and all facilities are operating normally.

ABC News' Alex Stone and Elizabeth McLaughlin contributed to this report.