Vehicle was parked at 10pm. Vehicle ignition was off. Vehicle was locked. Nothing left on. No one returned to the car for annything. Approximately 3 and half hours later, electrical fire started inside the drivers side rear quarter panel under the taillight (on the body, not the taillight on the lift gate) . By the time the car alarm was heard, the fire was spreading from the panel into the rest rear of the vehicle. Fire department arrived and extinguished the fire.