GRANTS PASS, Ore. (AP) — Just how a patch of genetically modified wheat wound up in a farmer's field in northeastern Oregon last spring remains a mystery. Speculation ranges from saboteurs to a passing flock of geese, and the U.S Department of Agriculture's Animal and Plant Health Inspection Service said Friday their investigation is continuing.

The unapproved wheat was found in May when the farmer sprayed his field with herbicides and a patch of wheat didn't die. The discovery was viewed as a potential threat to trade with countries that have concerns about genetically modified foods.

Blake Rowe of the Oregon Wheat Commission says although Asian buyers stopped placing orders for a couple of months, the overall economic impact has been minimal, and markets are back to normal. Area farmers plan to start planting their next crop in mid-September. If any more genetically modified wheat is growing, they won't know until spring.