Taco Bell's Suspect Shells

The federal government is investigating allegations that a genetically engineered form of corn approved only for animals was used in making Taco Bell tortilla shells sold in supermarkets.

While there are no known reports of injury, this finding—by the coalition Genetically Engineered Food Alert—is the most serious evidence so far of the potential risk in gene altered food, reports CBS News Correspondent Wyatt Andrews.

The Food and Drug Administration, which is now rushing to test this corn, says it has no reason to believe its unsafe.

But neither the government nor the biotech industry has ever conclusively proven the danger or safety of the corn involved. Produced by Aventis Corp., the corn—called StarLink—was approved by federal authorities in 1998 only as animal feed.

Coalition demands recall

The coalition is demanding the government order a recall, and says samples of taco shells from Taco Bell restaurants will be tested soon.

Larry Bohlen of Friends of the Earth, a member of the coalition, said, "We're saying the FDA should use their authority and seize the product."

"This is a possible allergen illegally on the market," said Jane Rissler of the Union of Concerned Scientists.

Federal officials called the possibility that the modified corn had been made it into food products "very serious" if confirmed by further testing.

"If there has been a violation of our licensing process, then we would have a very great concern," Stephen Johnson, an assistant administrator for pesticides at the Environmental Protection Agency, told The Washington Post, which broke the story.

"Likewise, we would want to make sure we are completely protecting the public health," he said.

FDA officials say the possible presence of StarLink corn in human food is "unlawful."

While the biotech industry argues that StarLink is safe, the Environmental Protection Agency disagrees, saying "information…indicates that Cry9c exhibits some characteristics of known allergens."

Because the corn has been genetically modified in a way that makes it more difficult to break down in the human gut, federal agencies have refused to approve it for human use.

Kraft is investigating

The taco shells tested were manufactured in Mexico for Taco Bell and were distributed by Kraft Foods Inc. Taco Bell is owned by Tricon Global Restaurants Inc., and Kraft is a unit of Philip Morris Cos.

The Post quoted Michael Mudd, Kraft's vice president for corporate affairs, as saying that the corn was bought by a Texas miller from farmers in six states and that the miller had ordered a conventional form of corn.

"This is a serious issue, and Kraft is doing everything w can to confirm whether or not this material is present in the product," he said. "If it is confirmed, we will immediately take, in consultation with the FDA, all appropriate steps."

But while Kraft foods says it will immediately "investigate and test" for contamination, it will not order an immediate recall.

One reason is that the food industry believes the Iowa lab that did the taco test, Genetic ID, is biased against biotech products.

At least once before, the company came to conclusions about the presence of genetically modified materials that were later proved inaccurate, according to The Washington Post, which broke the story.

Anne Heagert, a spokeswoman for Genetic ID, told CBS News, "We found the DNA of the variety of corn that contains that protein, without any doubt."

While most of the U.S. political, scientific and commercial establishment has embraced biotechnology as safe and useful, activists continue to raise questions about its use and hope to nspire the kind of widespread backlash present in Europe.

If proved true, the Taco Bell finding could be a windfall for those biotech critics.

"We do see it as a warning signal to the American public that there's no adequate system to look out for these genetically engineered ingredients," said Bohlen.

The StarLink corn is genetically modified to contain the plant pesticide Bacillus thuringienis, or Bt, which kills the destructive European corn borer. While there are many varieties of Bt corn now, StarLink is the only one that contains the Cry9C protein, which federal officials have concluded might cause an allergic reaction in some people.

However, some studies indicate that, by all available evidence, StarLink is safe.

In a 1999 memo to the EPA, Aventis admitted "there are currently no validated models for the prediction" of whether a particular food will cause human allergies, which 1 to 2 percent of humans have.

But, Aventis argued, StarLink is probably safe because its source material hasn't been found to cause allergies, mice and poultry fed StarLink corn feed didn’t get sick, and "Corn has no known history of food allergy."

More from CBS News