On Monday, investigators working with the US Department of Agriculture's plant inspection agency APHIS released the first progress update in nearly two months on the search for the source of genetically modified wheat found growing in a farmer's field in Oregon.

USDA personnel have been investigating the incident, as well as searching for other GM plants which could have outcrossed into the wild, for almost three months, but APHIS had little new information to report on Monday. The Agency did reveal that no GM wheat has been detected in commercial supplies, and that no other plants have been found growing wild.

The wheat was discovered in early May when an anonymous farmer raised the alarm after treatment with glyphosate failed to kill off wheat volunteers in a field in Eastern Oregon. Laboratory testing revealed the wheat was a GM glyphosate-resistant variety (MON71800) trialled extensively by agribusiness Monsanto between 1998 and 2005, but scrapped before it was commercialised or fully licensed due to resistance from farmers and consumers.

The resulting scandal saw many of the US' trade partners in East Asia suspend imports of white wheat grown in the Pacific Northwest region, principally for the Asian market. US authorities agreed to share their testing methods to help importers ascertain whether the wheat was present in any shipments. So far, no traces have been detected; South Korea lifted its restrictions several weeks ago, and Japanese officials confirmed on Monday that trade with the US could resume as early as this week.

Even so, APHIS said on Monday (29 July) that "Extensive testing following the detection of these plants" has yet to shed any light on the provenance of the GM wheat. Although investigations to determine the extent of the wheat's spread have uncovered no other MON71800 plants, expert scientists have publicly challenged Monsanto's assertions that the isolated discovery was the work of anti-GM activists, seeking to destabilise the biotech industry.

Some have said that the possibility of GM traits escaping into the natural environment is an inevitable risk of conducting open air GM trials.   

As part of the investigation, APHIS has "re-reviewed" its authorisations involving MON71800 field trials and related field test reports, which the agency believes could help in discovering the origin of the GM wheat. 

An APHIS spokesperson said, "All of the evidence collected thus far – specifically, the absence of MON71800 in seed and grain samples tested by USDA laboratories, and reports from nearly 270 farmers interviewed by USDA investigators that they have not observed glyphosate-resistant wheat plants in their fields – indicates that the extent of the presence of this [GM] wheat remains the single detection of the wheat plants in one field of one farm in Oregon."

The spokesperson continued, "We are moving forward with the investigation as expeditiously as possible. As necessary, we will take appropriate remedy measures and enforcement action."