Maybe a BOOM, but not a KABOOM!
I've seen numerous photos of gas explosions in houses that left nothing standing above the foundation. This wasn't a single family house -- looks like it was a duplex, probably a condo, in a community of such duplexes. The explosion lifted a part of the roof over the side that was already on fire, and blew out the garage door. Doesn't appear that the explosion did much of anything to the unit on the right (although I'd expect some broken windows and melted siding). Doesn't appear to have affected the attached unit to the left at all.
I don't think it could even have been a 25-pound propane tank for a gas grill. I'm thinking more like one of the small propane tanks for hand-held soldering torches.