The European Commission is considering halting the import of genetically modified corn gluten feed from the United States in a row with a Swiss agrochemicals group.
Syngenta disclosed in March that some of its maize seeds were mistakenly contaminated between 2001 and 2004 with Bt-10, an insect-resistant strain that was not approved by the European Union for distribution.
The unauthorised maize strain entered EU markets as seed, food and animal feed via exporters in the United States where Bt-10 got mixed with another strain, Bt-11, which is approved.
The European Commission wants Syngenta to help it identify Bt-10 so the 25-nation bloc can differentiate the two types of biotech maize and trace the tainted consignments but Syngenta has so far refused to give the information.
"The Commission is reflecting about possible action . . . a temporary suspension of imports of corn gluten feed," said an EU official.
Some 1,000 tonnes of Bt-10 maize entered the EU as food and animal feed, and 10 kilograms of seeds were planted in France and Spain in research field trials that were then destroyed.