SHELL ROCK — Investigators have not yet determined the cause of a Saturday afternoon explosion and fire at the Poet ethanol plant in Shell Rock.

Witnesses reported seeing a fireball at that time and felt the explosion for a radius of several miles around the plant. Butler County Emergency Management reports that by the time emergency crews arrived on the scene, the fire had taken care of itself.

No one was injured in Saturday’s fire. The cause is under investigation, but authorities say one possibility was a combustible dust explosion.