CAMBRIA, Wis. — Recovery crews searched a mountain of debris for two workers Thursday following an explosion at a corn mill plant that killed at least one employee, injured about a dozen others and leveled parts of the sprawling facility in southern Wisconsin, authorities said.

Sixteen employees were working when the blast was reported around 11 p.m. Wednesday at the Didion Milling plant in Cambria, a small community about 45 miles northeast of Madison, Columbia County Sheriff Dennis Richards said during a news conference Thursday.

There was no immediate word on what may have caused the blast at the plant, which was cited in January 2011 for exposing its workers to dust explosion hazards, according to records from the Occupational Safety and Health Administration. The records state that plant filters lacked an explosion protective system.

The agency ordered the mill to correct the problem by April 2011. The records show Didion paid a $3,465 fine and the case was closed in September 2013. OSHA hasn’t cited the plant for anything since, the records show. The plant processes corn for ethanol and other uses.

E-mails sent to several company officials Thursday and a voicemail left for Vice President of Sales Jeff Dillon weren’t immediately returned.

Associated Press