Lithium-ion battery fires are dangerous, but small batteries alone don't usually cause this much damage.

Both Wiens and MG said a supply-chain attack in which a remote-triggered explosive was surreptitiously placed into the pagers before they were distributed is more likely. There is precedent for this: in 1996, Israel put a bomb inside of a cell phone and used it to kill Yahya Ayyash, who was then a bomb maker for Hamas.