It is very common when gas equipment is stolen or otherwise removed that the uncapped gas lines leak gas. I have seen this literally hundreds of times. You are correct that Gasoline explosions in structures are rare, and they seldom exhibit "high order" damage. How would you characterize the damage, "high order" or "low order"? Have the closed valves been actually tested to see if they were actually or fully closed?
Pat
Pat Kennedy, CFEI, CFPS, MIFireE
Fire and Explosion Analyst
Sarasota, Florida
[
www.kennedy-fire.com]