A variety of genetically modified corn not permitted in food has been detected in taco shells sold in U.S. grocery stores under the brand name Taco Bell, according to test results released by the Genetically Engineered Food Alert, a coalition of enviro, health, and consumer groups. Government officials are investigating the charges. The corn, which is genetically engineered to kill an insect, is approved for use in animal feed but not in human food because of concerns that it could trigger allergies and because it has been modified in such a way that the human body has difficulty breaking it down. GE Food Alert is calling for an immediate recall of the taco shells, which are distributed by Kraft. The group says that the finding is potentially “the tip of the iceberg” and that the banned corn could be in a number of other products as well.