Unapproved genetically engineered wheat has been found growing on a farm in Oregon, federal officials said Wednesday, a development that could disrupt American exports of the grain.

The Agriculture Department said the wheat was of the type developed by Monsanto to be resistant to the herbicide Roundup, also known as glyphosate. Such wheat was field-tested in 16 states, including Oregon, from 1998 through 2005, but Monsanto dropped the project before the wheat was ever approved for commercial planting.

The department said it was not known yet whether any of the wheat got into the food supply or into grain shipments. Even if it did, officials said, it would pose no threat to health. The Food and Drug Administration reviewed the wheat and found no safety problems with it in 2004.

Still, the mere presence of the genetically modified plant could cause some countries to turn away exports of American wheat, especially if any traces of the unapproved grain were found in shipments. About $8.1 billion in American wheat was exported in 2012, representing nearly half the total $17.9 billion crop, according to U.S. Wheat Associates, which promotes American wheat abroad. About 90 percent of Oregon’s wheat crop is exported.