Engine by gas station appears to be relatively intact, suggesting it came off at the mounts rather than 'blowing up.'
There was an area on the engine casing that appeared to have a peculiar half-circle 'spiderweb' fracture. A fireman was taking notes on that area. Cannot speculate on whether the engine casing got that fracture on impact or prior to impact, but the fracture looks like an impact (caved in) rather than tensile fracture on the side. It could be the engine, after torquing off its mounts, struck something as it was falling.
Another (?) engine appeared to have come through a three-story Victorian home -people OK- demolished the home in back and went into a boat in the back yard, where it erupted into flames. I haven't seen engine #2 on film.
Engines when the come apart will lose turbine blades and these could fly into the fuselage, which could seem like an on-board explosion. An engine coming off its mounts could also make a sound like an explosion that would be noticed before anyone would notice the engine itself. If it came apart at the mount the engine would remain relatively intact.
One doozy of a fire there.