US agriculture giant Monsanto, in the spotlight over the discovery of unauthorised genetically modified wheat growing in Oregon, said on Wednesday it has a new GM wheat strain under development.

The company is developing a new form of Roundup Ready wheat, resistant to Monsanto’s herbicide Roundup (glyphosate) and also focused on improving yield, Robb Fraley, the firm’s chief technology officer, said in a conference call with reporters.

Claire Cajacob, head of Monsanto’s wheat research, said the company was testing a genetically modified, or genetically engineered, spring wheat in North Dakota, adding that field tests started in 2011.

Monsanto stopped testing its original Roundup Ready wheat strain in 2005 amid market concerns about the acceptance of GM products.

But it pushed back into the field in 2009, resuming work on wheat with the purchase of WestBred, a biotech wheat developer.

Monsanto’s original Roundup Ready GM wheat strain, though approved as safe by the Food and Drug Administration, was not authorised for commercial use at the time Monsanto ended the tests.

But the US Department of Agriculture announced a week ago that it was found growing in an Oregon field by a farmer.

That rattled export markets sensitive to genetically modified organisms, and Japan suspended imports of some US wheat, as did South Korean millers. In Europe meanwhile officials said they would check US imports for signs of the GM wheat.

Monsanto officials were unable to offer an explanation of how their original Roundup Ready wheat was growing in Oregon, but said they were cooperating fully with the USDA investigation of the incident.

To the best of their knowledge, the officials said, the original Roundup Ready wheat seeds were either destroyed at the end of the program in 2005 or stored in a USDA facility in Colorado.

The company said it was not ruling out the possibility that the GMO seed was accidentally or purposely mixed in the seed the farmer planted.

Asked whether Monsanto was considering the possibility of sabotage, Philip Miller, Vice-President of Regulatory Affairs, said: “That’s certainly one of the options we’re looking at.”