Firms representing farmers who in a lawsuit alleged economic damage from the commercial U.S. release of two GMO corn varieties said Thursday that more farmers – now representing 20 states – have joined the suit.

First filed on Nov. 11, the suit alleges that Syngenta – marketer of two GMO corn varieties unapproved for import in China, a major U.S. commodity buyer – wrongfully handled release of the traits for commercial use in the U.S.

China detected the presence of one of the traits, Agrisure Viptera (MIR 162), in cargoes of American corn last November. This caused the country to halt all corn shipments from the U.S.

Law firms amend previous suit against Syngenta to include 20 states; say Syngenta's release of two GMO corn varieties depressed corn market

Related: NGFA: China's MIR 162 Rejection Has Significant Impact on U.S. Grain Sector

Farmers filing the suit say the loss of the Chinese marketplace damaged prices for corn.

Though the trait has successfully completed the U.S. approvals process, the farmers say Syngenta was aware of the potential damages from marketing the grain before it was approved for import in China.

The expanded suit comes as USDA Secretary Tom Vilsack was quoted this week in reports from both Reuters and Bloomberg indicating that Chinese authorities have approved the MIR 162 trait for import. No official word from the U.S. or China, however, has been released.

Also Wednesday, Syngenta reportedly dropped a separate lawsuit against grain trading company Bunge, which has refused to accept shipments of Viptera corn since 2011, Reuters said.

Other lawsuits from grain shippers and key grain industry player Cargill, like the 20-state farmer suit, still center on damages from the trait's release in the U.S. market.

A member of the farmers' group of law firms alleged that Syngenta wrongly said the MIR 162 release would not impact export markets.

Related: Agribusiness Industry Presses Obama on Chinese Biotech Policies

"It was wrong and we believe Syngenta did not take the necessary steps," William Chaney of law firm Gray Reed said in a press statement. "The farmers and the industry as a whole have been damaged and this suit seeks to hold Syngenta accountable for that damage."

Syngenta, in response to the lawsuits, said they are "without merit" and MIR 162 provides major benefits for growers, including prevention of yield and grain quality losses from pests.

The company also notes that the commercialization of the trait was completed in full compliance with regulatory requirements.

The other trait in question in the farmers' lawsuit is Syngenta's Agrisure Duracade. Reuters reports China already has approved about 15 other GMO crop varieties for import, though its sluggish approval process has been the subject of much concern among U.S. farm groups.

For commentary on the lawsuits mentioned, see Ag Attorney Gary Baise's September blog entry, "Corn Wars: A Legal Battle Over GMO Traits."