It's not an accident; it's a riot.
Strange people with the sharp faces of Forte are chanting, and although they are still too far away to make out the words clearly over the roar of flames Viola can guess what they're yelling. Mineral powder. Mineral powder!
They're burning the forest down in an vain attempt to continue mining land that has nothing left to give, dying people desperate for the drug that would kill them. They don't know how to cope without the pseudo-medicine they'd been addicted to for gods only knew how long—and gods only knew what they'd do to get it.