Investigation continued this week into how understand genetically modified wheat ended up on a farm in Oregon
No varieties of GM wheat have been cleared for commercial use anywhere
the wheat plants in question are believed to be the legacy of a research programme that was abandoned nine years ago
how and why they have resurfaced is unclear
The discovery last week triggered an international reaction, with both South Korea and Japan temporarily suspending imports of US wheat.
South Korea has also begun testing existing wheat imports from the US for signs of GM wheat, with no positive results so far