Syngenta has sued several grain trading firms, saying it was their fault that Chinese authorities halted U.S. corn shipments during 2013 and 2014. The halt occurred because the shipments contained traces of a Syngenta genetically modified corn that was not yet approved for sale in China. Syngenta filed its suit in the U.S. District Court of Kansas. The shipping firms as well as farmers are already suing Syngenta for more than $1 billion in damages because of lost export revenue. The seed company contends that the grain traders, including Cargill and Archer Daniels Midland, should have kept its Viptera corn separate instead of mixing it with the general U.S. corn supply. Viptera is engineered with a trait called MIR162 so it can produce a Bacillus thuringiensis protein toxic to caterpillars and other insects. USDA approved the sale of Viptera in 2010. Despite warnings Syngenta says it gave to the grain traders, they still shipped corn containing Viptera to China. If the farmers succeed in their suit, Syngenta wants the trading firms to bear liability for damages.