Afterthought: the a/c did have about 30 or so high tech people on board who collectively would have had a significant amount of L-I batteries either in cabin or in hold or a mixture.
You don't need techies on board for that. Just think of all the laptops, smartphones, tablets and the like that pax carry with themselves in any normal flight. Nearly all of them have Li-Ion battery packs.
Anyway, it's extremely unfrequent that they ignite/explode, but if that happened in cabin (i.e. when stowed in the luggage compartments together with coats), there would be a problem...