Sounds like a gas explosion.
I think you’re right.
I guess gas explosions can be different from one another, but I witnessed one once. Instead of the “crack” sound of a high explosive, there was a deep powerful “boom” accompanied by a low pressure pulse, like one of those obnoxious automobile subwoofers. The townhouse just sort of expanded and blew wallboard and bricks fifty feet into the air. Bits of paper and insulation were raining down for a minute or more. There was no flame afterward.