An unapproved variety of genetically engineered glyphosate-resistant wheat was found in samples taken from a farm in Oregon, according to the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS).

The variety detected was the same one Monsanto grew in test plots in 16 states from 1998 to 2005, known as MON71800. There are no genetically engineered wheat varieties currently approved for sale in the U.S. or any other country.

USDA Office of Communications Director Matt Paul said the wheat variety does not pose a public health or food safety concern. “Monsanto worked with FDA in 2004 to complete a voluntary food and feed safety consultation. Completion of the FDA consultation process means this variety is as safe as non-GE wheat currently on the market.”

USDA began investigating the matter on May 3 when an Oregon State University scientist notified agency officials that plant samples had tested positive for a protein that made them resistant to glyphosate.

“As of today, USDA has neither found nor been informed of anything that would indicate that this incident amounts to more than a single isolated incident in a single field on a single farm,” he continued. “All information collected so far shows no indication of the presence of GE wheat in commerce. Investigators are conducting a thorough review. They have interviewed the person that harvested the wheat from this field as well as the seed supplier who sold the producer wheat seed; obtained samples of the wheat seed sold to the producer and other growers; and obtained samples of the producer’s wheat harvests, including a sample of the producer’s 2012 harvest. All of these samples of seed and grain tested negative for the presence of GE material. Investigators are continuing to conduct interviews with approximately 200 area growers.”

On June 13, USDA validated an event-specific PCR (DNA-based) method for detecting MON71800 (provided by Monsanto to USDA on May 23). The USDA validation process included a specificity study and a sensitivity study. USDA determined that the method can detect MON71800 reliably when it is present at a frequency of 1 in 200 kernels. Additionally, USDA has provided this validated DNA test method to detect this specific GE variety to trading partners that have requested it.

Major markets, such as Japan, Korea and Taiwan, postponed imports of U.S. white wheat as they continue to study information from U.S. officials to determine what, if any, future action may be required.

The Non-GMO Project responded to the incident immediately by coordinating its own surveillance testing strategy to help assess the extent of the contamination. The testing plan includes sampling wheat products from the national retail market as well as raw plant material directly from Oregon.

This is not the first time a U.S. crop has been contaminated by an unapproved GMO. Most notably, in August 2006 the USDA announced that Bayer’s genetically engineered LibertyLink rice was found in two popular varieties of U.S. long-grain rice. The discovery led to rejection by foreign markets and a corresponding dramatic decline in U.S. rice prices. The LibertyLink contamination eventually resulted in a $750 million legal settlement between Germany-based Bayer AG and its affiliates and U.S. rice farmers. According to the Delta Farm Press, European Union purchases of U.S. rice remain only a small fraction of what they were before the 2006 incident.

The U.S. wheat market has similar vulnerability. According to the Oregon Wheat Commission, Oregon exports 90% of its wheat production. More than 60 countries now require labeling of GMOs, and international regulations on import and sale of unapproved GMO varieties are strict.