The European Union has adopted a "zero tolerance" policy when it comes to genetically modified crops, and its consumer protection office said it would be testing its shipments for any modifications, as well as seeking "further information and reassurance" from Washington.
The strain in question had been genetically altered to withstand the Roundup herbicide.
On Thursday, the U.S. Wheat Associates and the National Association of Wheat Growers sought to tamp down the concern, saying there is no good reason for other nations to block U.S. wheat.
"There is no reason for governments to establish a restriction on U.S. wheat as the USDA made it clear yesterday that there is no evidence suggesting that this material has entered commercial supplies and that there is no health risk associated with it," the groups said in a statement.
They added that they were working with U.S. and Japanese authorities to address the issue, saying that "nothing is more important than the trust we've earned with our customers at home and around the world."