A well aimed shot from a 50 cal.? An RPG shot from the motorway? A mortar? A plug of Semtex? A Muslim suicide bomber?
An RPG shot from the motorway? Something along that nature. Close to freezing temps and you would be hard pressed to ignite gasoline let alone get it to explode. Explosions require massive vapors and cold temps keep that in check. Kerosene is very explosive when heated but I have heard of no reports of fire before the explosion.