Monsanto executives described the discovery of genetically modified wheat growing in an Oregon farmer’s field this spring as an “isolated occurrence.”

During a conference call with reporters, Monsanto officials said the company has tested 31,200 seed samples in Oregon and Washington since the May 29 announcement of the GM wheat sprouts. They found no evidence of contamination in the tests and said the GM wheat found last month was likely the result of an accident or deliberate mixing of seeds. They are not ruling out sabotage.

“We’re considering all options and that’s certainly one of the options,” says Robb Fraley, Monsanto chief technology officer. Fraley said Monsanto provided a test to other countries that could “fingerprint” the exact variety of wheat that carried the GM gene, and it is awaiting samples from the U.S. Department of Agriculture or the Oregon farmer to test for the exact variety that emerged.

Monsanto is a $13.5 billion St. Louis-based company with revenues anchored in sales of GM corn, soybean and cotton seeds that have been engineered to survive applications of Monsanto’s Roundup, the world’s top-selling herbicide.

Officials estimate that 90 percent or more of U.S. soybeans and 80 percent of U.S. corn are “Roundup Ready,” or genetically modified. The success of those crops led Monsanto to begin work on GM wheat, but the company ended the program nine years ago when executives determined resistance to GM crops by consumers and export customers would hurt demand for the seed.

Since that time, Monsanto has come under increasing criticism for its role in developing and marketing GM crops. Several countries ban the use of GM crops, claiming the risks to humans are unknown. G.H.