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

During a conference call with reporters on Wednesday, 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.

Other critics and many activists claim food made from GM crops are dangerous to human health, and Monsanto is regularly singled out as an “evil corporation.” For instance, published results from an online survey in January, 2011 in which 51 percent of respondents called Monsanto the “Most Evil Corporation of the Year.” NaturalNews Network is owned and operated by Truth Publishing International, Ltd., a Taiwan corporation, that claims to cover topics that “empower individuals to make positive changes in their health, environmental sensitivity, consumer choices and informed skepticism."

Such perceptions of Monsanto - the world's largest seedmaker - by environmentalists, food activists and others, helps spur global protests over GM foods and fuels concerns by the company that sabotage could have been involved in the Oregon incident.

Following the end of the GM wheat program in 2005, Monsanto says all of the tested GM seeds were either destroyed or recovered and sent to a USDA facility in Colorado for storage. Monsanto’s Fraley said that because those Roundup-resistant plants existed on only one of two of the Oregon farmer’s fields and haven’t sprouted on other farms since 2005, the occurrence is either “inadvertent or purposeful mixing of seed.”

Monsanto officials said the average wheat seed only stays viable for one or two years in a harsh climate like Eastern Oregon’s, and that it’s unlikely that other parent stocks were corrupted.