GMO food has been controversial among consumers who have concerns about health, safety and environmental issues relating to the new technology. Now farmers are raising legal issues with one of the world’s leading suppliers of GMO seeds.

The agribusiness and biotechnology company Syngenta is being sued by about 2,000 farmers, grain dealers and food exporters, according to the New York Times. A federal judge this week denied Syngenta’s motion to dismiss the cases and said the plaintiffs can proceed with their claims against the Swiss-based company in U.S courts.

Genetically engineered, also called genetically modified (GMO) seeds are sold to farmers with promises of reduced costs and easier growing conditions. But the farmers fighting Syngenta say that the company sold them GMO seeds for a variety of corn that was not approved for export to China.

The U.S. exports billions of dollars worth of corn to China each year. When Chinese authorities found the unapproved Syngneta GMO corn from the U.S. in 2013, they rejected the shipments, costing farmers and the corn industry billions in lost sales.

In addition, the drop in the commodity market price for corn following China’s reaction also led to major losses. In total, the plaintiffs say that the GO contamination episode cost the U.S. corn industry as much as $3 billion.

Syngenta argued that the case should be dismissed because the company has no duty to protect farmers or grain industry businesses. But the judge rejected the company’s plea. More than 1,860 cases from 22 states have already been certified, with another 500 or more having been filed just since September.

Syngenta’s GMO corn, marketed as an insect-killing variety called Agrisure Viptera, was approved by U.S. regulators in 2010. But the GMO variety was not approved for export to China, so when testing uncovered the GMO corn in shipments sent to that country in November 2013, China took action. By February 2014, China began rejecting U.S. corn shipments, altogether turning back more than 131 million bushels of corn.

The judge in the case against Syngenta is also expected to rule on whether the cases can go forward as a class-action case. If such a ruling is forthcoming, experts say the case would be the largest such agricultural lawsuit in history.