Prosecutors say thousands of individuals and businesses were victims of a large-scale scheme in which ordinary corn and soybeans were fraudulently marketed nationwide as "certified organic."

The U.S. Attorney's Office in Cedar Rapids, Iowa, said in a filing Wednesday that potentially "tens of thousands" were defrauded by Randy Constant and his associates into paying a premium for products that they didn't want.

Constant, of Chillicothe, Missouri, and three others have pleaded guilty and are awaiting sentencing. Constant, who owned an Iowa grain brokerage, acknowledged that he sold $142 million worth of corn, soybeans and wheat over a 7 ½ year period that wasn't organic despite his representations.

Constant was aware that most of his product was grown using non-organic methods. The buyers included companies that processed the grain into other products that were marketed as organic.