I am performing a private origin and cause investigation of a fire in an older ballon construction vacant two story house. This house is in a block that has had 4 other house fires. There are some turf wars going on in this neighborhood. The neighbor heard a loud boom and looked out his window and saw some individuals driving out the driveway between the houses and the house next door on fire.

The kitchen on the first floor in the rear suffered the worst fire damage. The roof had collapsed into the kitchen. The back wall to the kitchen had blown out into the back yard. There were no appliances in the kitchen. The entire house had extensive fire damage.

The outside side walls were bowed outward. The basement had concrete walls with about 4 feet of the basement above ground. The concrete wall that was above ground was cracked all the way around the basement at ground level and pushed outward. The basement had glass block windows and they were all blown outward as well.

The furnace and hot water heater had been stolen approximately a week before the fire. The utilities were still intact. At the time of my investigation the gas lines in the basement were still intact with the valves in the closed position. There was an enclosed stairwell to the basement and the first floor in the rear corner of the house. The side exterior wall to the stairwell at the top of the basement steps was blown outward.

My initial thought was that a gas line had been opened and ignited by some unknown ignition source. I thought the main body of gas was in the basement because of the basement walls pushed out and the wall at the top of the steps blown out.

I contacted the fire officer on the Truck company. He stated that upon arrival there was fire coming from every opening. He stated he did not smell any natural gas and had no knowledge of a gas fire after their arrival.

I have seen both natural gas explosions and gasoline accelerated fires during my career. But I have never seen a building explode from gasoline fumes. I would like to know if this sounds like a natural gas explosion or how possible gasoline fumes caused the explosion. I did not take samples assuming it was natural gas explosion but after talking to the fire officer I began to wonder. Your opinion would be very helpful.

Thanks.