Wheat prices tanked Thursday after Japan suspended imports from the U.S., citing the discovery of Monsanto-developed wheat growing in an Oregon field.

The European Union is suggesting that its 27 member states test wheat that comes from the United States after genetically engineered grain was found on a farm in Oregon.

On Thursday, Japan halted imports of certain types of wheat from the U.S. following the discovery of an experimental strain that was tested by Monsanto but never approved.

Monsanto had stopped testing genetically engineered wheat in several states in 2005.

The EU’s consumer protection office said Friday that shipments which test positive should not be sold in line with the bloc’s “zero tolerance” for GM crops.

It also said it was seeking “further information and reassurance” from U.S. authorities and had asked Monsanto for help in developing a reliable test for the GM grains.

The European Union imports more than 1 million metric tons (1.1 million tons) of U.S. wheat each year, mostly to Spain.