Genetically modified wheat was discovered recently on an Oregon farm when a farmer tried to spray some volunteer wheat that wouldn't die.
The farmer reportedly sprayed volunteer wheat sprouts with glyphosate, a broad spectrum plant killer, and some sprouts unexpectedly survived, according to a report by the Drovers Cattle Network.
GM wheat had not been approved for farm use in the United States.
The Drover's Network said scientists found the wheat was a strain that was field-tested from 1998 to 2005 and deemed safe, before Monsanto withdrew it from the regulatory approval process.
A lawsuit is underway against Monsanto, an international company that makes genetically modified crops, claiming Monsanto negligently damaged the value of farmers' wheat crops.
GM corn, soybeans and cotton are widely used in the United States but not in other countries.
After news of the GM wheat discovery, Japan and South Korea suspended purchases American wheat, and the European Union, which imports more than 1 million tons of U.S. wheat each year, said it would ensure its “zero tolerance” policy against GM crops was maintained, the Drover's Network said.