Two days after a horrific explosion at a biofuels plant left a man and two girls dead, the state fire marshal told First Alert 6 the incident started with a dust fire — and was an accident. “A preliminary investigation indicates an accidental dust explosion occurred during the manufacturing process.

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

In a press release on Thursday, officials said there was an accidental dust explosion at Horizon Biofuels during the manufacturing process.