In this Feb. 7, 2007 file photo is the headquarters and logo of the Swiss chemical maker Syngenta in Basel, Switzerland. More than 360 lawsuits have been filed by farmers and farm businesses in U.S. 20 states in a legal dispute centering around Syngenta's sale of a corn seed called Agrisure Viptera, which was genetically altered to contain a protein that kills corn-eating bugs such as earworms and cutworms. (AP Photo/Keystone, Georgios Kefalas, file)

(AP)—Farmers and farm businesses in 20 states have now filed more than 360 lawsuits against agricultural chemicals-maker Syngenta, and hundreds more may be coming as a federal judge organizes the complex case so they can move forward.

The dispute centers around Syngenta's sale of a seed called Agrisure Viptera, which was genetically altered to contain a protein that kills corn-eating bugs such as earworms and cutworms. The U.S. Department of Agriculture approved it in 2010, and Syngenta first sold it to farmers in 2011.

China, a growing importer of U.S. corn that refuses to buy genetically modified crops it hasn't tested, had not approved Viptera when Syngenta began selling it. In November 2013, China discovered the Viptera corn trait in several U.S. shipments.

It began rejecting U.S. corn imports in February 2014. The lawsuits say it rejected more than 131 million bushels.

Loss of revenue to the U.S. corn industry has been estimated by the National Grain and Feed Association, a trade group, at between $1 billion and $3 billion. Farmers who did not plant the Syngenta seed, grain handlers and exporters claim they lost money because of the Chinese boycott of U.S. corn and corn byproducts.

"Knowing that contamination of Viptera corn with the rest of the U.S. corn supply was inevitable, Syngenta nevertheless gambled U.S. farmers' livelihood on approval of Viptera by the major corn-importing countries," according to a lawsuit filed Jan. 13 in federal court in Iowa by Thomas Land and Livestock Corp., a business in east-central Iowa.

Lawsuits making similar claims have been filed in corn-growing states including Illinois, Iowa, Missouri and Nebraska with hundreds more being prepared, plaintiffs' attorneys say. Some suits are from farmers represented by individual attorneys, others are class-action lawsuits. Agribusiness conglomerates such as Cargill and ADM, which export grain, also have sued, claiming their businesses suffered losses. Cargill's estimate is more than $90 million.

A panel that manages lawsuits involving large numbers of plaintiffs has assigned Senior Judge John Lungstrum in Kansas City to oversee all of the cases filed from around the country in a consolidated action.

Cargill, which said it supports development of new GMO products, claimed Syngenta selling Viptera before obtaining import approval from major markets was "inconsistent with industry standards and the conduct of other biotechnology companies."

Syngenta has said it plans to ask the court to dismiss the farmer lawsuits because "plaintiffs do not and cannot point to any authority barring the introduction of a U.S.-approved product in the U.S. simply because the product was not yet approved for sale in a foreign country like China."

"In short, this litigation constitutes an unprecedented effort to hold a company liable for selling a U.S.-approved product in the U.S., simply because the product was not yet approved by a foreign country like China," lawyers for Syngenta wrote in a Jan. 14 court filing.

A spokesman for Syngenta, which is the world's largest crop chemicals company, did not respond to messages seeking comment. The Switzerland-based company, with annual revenue of about $15 billion, has an agricultural seed division based in Minnetonka, Minnesota.

China approved Viptera for import in December, but Kansas City lawyer Richard Paul said that doesn't change the assertion that farmers lost money. Paul, who represents clients suing Syngenta and serves on an executive committee of lawyers coordinating all the plaintiffs' cases, said China's approval may establish a definite period of time in which damages can be assessed, but the extent of financial harm may not be over.

"The approval is not the end because markets haven't fully recovered. Obviously that helps, but even though China is now accepting Viptera it has not restored its important levels to pre-ban," he said. "We'll have to see where it goes from here but it certainly does help put a cap on it and hopefully at some point here the markets recover."

Additional cases are still being transferred into the consolidated docket in Kansas City. Jayne Conroy, a New York attorney on the plaintiffs' executive committee, said there could be hundreds or thousands more.

"They are still filing all the time," she said. "I have many clients that are not filed yet. We are gathering the data. There's no deadline at this point."