You light one of your firebombs and toss it at the base of the cave door. It explodes as it makes contact and engulfs the door in fire. It should only take a couple a minutes for the door to weaken enough for you to use the crowbar to smash through it. Meanwhile back at the basement, one of the firemen reaches the caves opening and notices a glow coming from deep inside the cave. He calls out on his radio that he's found some type of cave and asks for another fireman to come and take a look. Soon he is joined by another fireman and they radio back to the chief that they're going in to investigate.