1991 Volkswagen Jetta strange noise

I tried to start my car but the battery was dead. When I put the jumper cables on I began to hear a strange noise coming from the back underbody of the car like a low whirring noise before I even tried to start the engine. There was nothing on in the car. In about 5 minutes I began to smell gasoline. I think it was pouring out of a thin white tube on the front passenger side of the car under the air intake. I had to disconnect the battery to get the noise to stop and stop the gasoline from pouring out. The car has always ran good up til now. Any ideas?