In the latest potential sign of contamination from genetically modified crops, alfalfa plants in Washington state have tested positive for genetic modification, even though the farmer believed they were unmodified. Agriculture officials are testing the alfalfa after it was rejected for export by a broker. In May, genetically modified wheat created by Monsanto was discovered on an Oregon farm after the farmer attempted to kill the wheat with a Monsanto herbicide but found some of the plants had survived. Testing showed the wheat was from an herbicide-resistant strain that was field-tested before being withdrawn from the regulatory process after protests. The discovery prompted Japan and South Korea to temporarily halt purchases of some U.S. wheat.