The South Dakota Department of Public Safety has determined the cause of the Ringneck Energy Plant Explosion in Onida was accidental.
The investigation report suggests two separate explosions rocked the plant back in July, one in the southwest area of the plant and one in the southeast.
"Human involvement was a factor during the restart process form the shutdown of operations. By ramping up the restart process too fast and by-passing a valve interlock, there was high proof ethanol in the corn slurry tank," said Deputy State Fire Marshal Michael Jones .
He said both explosions were due to escaped ethanol vapors that found ignition sources.
No one was hurt in the explosion.
