Updated at 4:30 p.m.

Genetically modified wheat developed by Monsanto and never approved by federal regulators has been found growing in a Washington state farm field, the U.S. Department of Agriculture said Friday.

The discovery of 22 unapproved genetically modified wheat plants has prompted an investigation by federal and state agencies. It’s the third such discovery in three years.

A farmer found the GMO wheat in a field that has not been planted since 2015. The plants had been identified as being one of Monsanto’s experimental varieties “a few weeks ago,” a spokesman from the Washington State Department of Agriculture said.

The USDA is testing grain harvested from the farmer’s other wheat fields as a precaution, the agency said. Officials also reached out to at least one trade group earlier this week, and alerted importers on Thursday.

The grain has not been traced in commercial supplies, USDA said in a statement.