Gas likely methane leaked up from the tunnels and ignited by some kind of spark or flame. Engine or heating unit.
because this disrupted such a large area of cell phone and air traffic we shouldn't discount sabotage. though why the FBI is going after the owner of the RV when all they have to do is look at the cellar doors is what pisses me off about this. Any fire personal could've told them that. Its like they don't even ask questions.
However, there is the announcement that went on for a half hour or so before the explosion.
Christmas Eve night, only a few bars open, guy with no family, recently lost his last few relatives. Possibly, the RV guy finished drinking, and was sleeping it off in the RV.
The RV burned, it didn't explode. The explosion came from the open area of most concentrated gas, in front of the white car.
It is plausible that the RV was the source of ignition, but not the area of the heavy concentration of the gas. That was above the grates.
The twitter video shows clearly the red and white center of that concentration as the explosion begins.
Thank you. Gas build up is plausible. I was once in a store when gas build up caused a manhole to explode.
However, that doesn't explain the warning announcement and the real (or recorded) gunshots.