CAMBRIA, Wis. (AP) - The Wisconsin corn mill where an explosion late Wednesday killed at least one worker was cited by federal safety investigators six years ago for exposing workers to dust explosion hazards.

Records from the U.S. Occupational Safety and Health Administration show that Didion Milling Plant in Cambria was cited in January 2011 for exposing workers to hazards associated with dust explosion and other fire hazards. The records say filters in the plant lacked an explosion protective system.

OSHA ordered the mill to correct the problem by April 2011. The records show Didion paid a nearly $3,500 fine and the case was closed in September 2013. OSHA hasn't cited the plant for anything since.

Didion officials didn't immediately return messages from The Associated Press on Thursday. OSHA has launched an investigation into Wednesday night's blast.

Authorities say two workers are still missing and about a dozen other workers were injured