If a partial cause was lithium-ion battery banks, well, let’s just say they ALSO blow up real good, with not a lot of goading.. just my professional experience.
Instant hell on earth if enough go up, and it’s real hard to kill the flame.
IF it WAS a significant explosion, I would expect that, rather than a single high amplitude, sharp impulse, high VOD explosion like a penetrator bomb, big IED or a nuke, it was small "trigger" explosion(s) that set off something(s) already inside the facility, like you mention.
Instead of the sharp P-wave seismic impulse expected from a high-VOD explosion, I would expect a flame front that spread rapidly through the facility, overpressured it, and vented through the reverse-pressured blast door seals with a prolonged, "Whoosh!" that ejected a cloud of dark ejecta (heavy "soot") onto the surrounding surface. [Blast door seals are designed to keep high pressure OUT, rather than to keep it IN...]
That "flame front" would have produced a low-amplitude, long period seismic signal like a Rayliegh wave -- which would not look like an explosive "event" to short-period seismographs.