University of Arkansas graduate students sampled wild canola plants every five miles along 3,000 miles of roads in the state of North Dakota. Of 406 plants sampled, 80% of the plants had a minimum of one transgene attributable only to genetically modified canola plants. 46% of the stops found genetically modified canola plants.

This is described as the first time that genetically (transgenic) modified organisms have established a wild population in the U.S.

Source:

http://www.organicauthority.com/foodie-buzz/genetically-modified-organisms-found-in-the-wild.html

http://news.discovery.com/earth/gm-plant-canola-wild.html