While driving there were no warning indicator lights illuminated on the dash. He stated there were no mechanical defects, noises, or smells to be noted. Near Milepost [XXX] on [XXX] both occupants saw smoke begin to come from under the hood. The employee pulled the vehicle to the side of the road. Both employees exited the vehicle to open the hood. Employee stated he reached down to pull the hood release and when he looked up flames were visible above the hood. Employees moved away from the vehicle and called 911.