Farmers and major grain companies are suing Swiss biotech giant Syngenta over China's refusal to buy American GMO corn enhanced by the company.

China refused to buy corn from the United States in 2013 because it contained genetically modified seeds. That set off a rash of lawsuits by farmers and grain companies against Syngenta, whose seed was mixed with non-GMO corn in the U.S.

Dan Homolka, a Minnesota-based attorney for the farmers, told the Mankato Free Press that the co-mingling of genetically modified corn with non-modified caused China to turn around boat loads of corn and that's when the price started to drop.

"When the first bag of corn was rejected by China, corn prices started to drop. They started turning around barges of several million metric tons of corn," Homoka said.  

He is among several lawyers representing farmers and major grain companies in action against the Swiss biotech company.

"It was a co-mingling of a non-approved GMO that hadn't been approved by the Eastern Rim countries."

The modified seed, known as Viptera, was approved for planting in the United States in 2010 and Syngenta asked China to allow its import. Syngenta began selling the modified seed before China's approval and China cut off imports from America in 2013.

"It was approved in the United States, but it hadn't been approved in the market and (Syngenta) killed the market," Homolka said. "We're not anti-GMO corn lawyers. It's just an economic condition that occurred."

The seeds are genetically modified so that earworms and cutworms won't eat the corn plant.

The lawsuits alleged the plants from the modified seed cross pollinates with other corn plants, effectively causing the potential for all corn seed to be "contaminated."

The lawsuits claim China's ban cut U.S. corn exports by 85 percent.

Attorneys in the case say farmers nationwide lost an estimated $6.3 billion as corn prices plunged from about $7.50 a bushel to around $3.50 a year later.