The USDA says the discovery of genetically modified wheat in an Oregon field was an isolated incident.
Investigators say they have found no indication of the presence of the unapproved Roundup Ready wheat variety in commerce. All samples of wheat seed from the producer and seed supplier have tested negative. Investigators are continuing to conduct interviews with approximately 200 area growers.
The department has also validated a method for detecting the variety, and this test has been provided to foreign wheat buyers.
Japan, Korea and Taiwan have restricted imports of US white wheat as a result of the discovery.