I have read that the entire US corn crop has been contaminated with genetically modified corn. Today Naked Capitalism extracts data from a recent study on the toxicological effects of GMO corn. The study was conducted on rats.
The authors postulate that the genetically embedded pesticide and/or herbicide related genes in the corn are responsible for the observed toxicological effects.
Here is an excerpt from the conclusion:
"We therefore conclude that our data strongly suggests that these GM maize varieties induce a state of hepatorenal toxicity. This can be due to the new pesticides (herbicide or insecticide) present specifically in each type of GM maize, although unintended metabolic effects due to the mutagenic properties of the GM transformation process cannot be excluded."