The state fire marshal told First Alert 6 that Tuesday’s horrific explosion at a biofuels plant was started by a dust fire that led to the explosion — and was an accident.

Images taken after the Nebraska explosion show the plant's tall tower sheared off, exposing twisted steel and torn siding.

FREMONT, Neb. — Two girls were waiting for a relative to finish work at a Nebraska biofuel plant when all three were killed in a massive explosion that shook the town, officials said Wednesday.