When I hear about a house blowing up like this my mind immediately jumps to "meth lab" but I'd suspect that this would usually be pretty obvious to emergency responders. Given that they're saying it's okay for neighbors to return home I'm guessing that this wasn't the cause.
I guess that means a gas line fault is probably the most likely cause? I can't think of much else that would blow a whole house to bits, unless they were making bombs in there or something crazy like that.