South Korea has not detected genetically modified wheat in initial tests of imports of the grain and flour from Oregon, after news last week that a rogue strain of the crop had been discovered in the U.S. state spooked buyers globally.

Korean millers on Friday suspended imports of U.S. wheat until the final results of government tests on shipments from around the United States, now expected on Wednesday.

The wheat found in a northeast Oregon field in late April was developed by biotech giant Monsanto Co more than a decade ago but never put into commercial production.

The discovery of the long-forgotten strain prompted Japan to shun wheat from the Pacific Northwest at its weekly tender on Thursday, while some Asian countries ramped up inspections and the European Union said it would step up testing.

"Although our preliminary test result shows no genetically modified wheat was found, we are aiming to test all samples of wheat and flour imported from the U.S.," said an official at Korea's Ministry of Food and Drugs.

South Korea, which last year sourced roughly half of its total wheat imports of 5 million tonnes from the U.S., has also raised quarantine measures on U.S. feed wheat.

The U.S. has embraced genetically modified crops such as soybeans and cotton, however, genetically modified wheat has never been approved in the United States, or anywhere else in the world.