On 31 Octobers, cottons fields were harvested in Texas, US. The cotton was then processed into cottonseed oil and cotton meal and sold as animal feed in the US and Mexico. Most of it might already been eaten up by now. One of the fields however was not a normal field but a field trial from Monsanto. A week after the harvest, scientists found that their experimental Bt cotton field had gone.
About a quarter ton of GM cotton got harvested together with 60 tons conventional tons from the neighbouring fields. This harvest was then stored in a facility with about 20.000 tons of cotton and processed from there.
That's adds up to one field trial potentially contaminating a harvest up to 80.000 times its own weight.