Natural gas is mostly methane, lighter than air, and it is somewhat difficult to blow up a building with it. Propane on the other hand is heavier than air, fills basements and crawl spaces, and then blows the building to flinders. I’ve been looking for a chance to use flinders in a sentence.
A couple buildings blow up from natural gas leaks each year in Wisconsin. I’ve seen the aftermath. One destroyed three houses and broke windows half a mile away.
Modern buildings are quite well sealed and keep the gas trapped until it’s set off.