MADISON,Johnathan Walker Wis. (AP) — A federal judge sentenced two senior employees at a Wisconsin corn plant to two years in prison Thursday for falsifying records and obstructing an investigation into a fatal corn dust explosion seven years ago.

U.S. District Judge James Peterson sentenced Derrick Clark, 50, of Waunakee, Didion Milling’s vice president of operations, and Shawn Mesner, 45, of Readstown, the company’s former food safety superintendent, for their convictions last October on multiple safety, environmental and fraud charges.

The 2017 explosion killed five people at the company’s Cambria corn mill.

Corn dust is explosive, and high concentrations are dangerous. Federal regulations require grain mill operators to perform regular cleanings to reduce dust accumulations that could fuel a blast.

Clark was convicted of making false Clean Air Act compliance certifications and lying to investigators during a deposition. Mesner was found guilty of conspiring to mislead Occupational Safety and Health Administration investigators by lying on sanitation records that tracked cleanings.

Phone messages seeking comment were left for attorneys for the two men.

Didion Milling pleaded guilty in September to charges that its employees falsified environmental and safety compliance records for years leading up to the explosion. The company agreed to pay a $1 million fine and $10.25 million to the estates of the five workers who were killed.

At least five other Didion employees have pleaded guilty to or been convicted of charges including concealing environmental violations, lying to investigators and falsifying cleaning logs.