In a statement released Friday, Verasun, based in Sioux Falls, S.D., and one of the county's biggest ethanol producers, said it had lost between $63 million and $103 million in the second quarter due to margin calls to cover its futures positions as corn prices spiked sharply, The Des Moines Register reported.

Now it says it has hired an investment banking firm to help it find new equity partners. The company says it will continue to operate normally under the bankruptcy petition, which was filed in Delaware, the newspaper reported.

"Today's filing allows Verasun to address its short-term liquidity constraints as we navigate historically challenging market conditions while we focus on restructuring to address the company's long-term future," Chief Executive Don Endres said in a statement. "We appreciate the loyalty of our employees, customers and suppliers during this challenging time."