Officials said the team is concentrating on more than the two companies believed to have exported the melamine in wheat flour mislabeled as wheat gluten and rice protein concentrate.

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Examples cited in the announcement include the presence of substances new to the food supply, allergens presented in an unusual or unexpected way (such as a peanut protein in wheat) or increased levels of toxins found normally in foods.

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The former contained 20 percent protein, with egg, wheat germ, a seed mixture and more, while the latter contained only 8 percent protein.

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Gluten is a protein found in wheat, barley and rye (the wheat version gets most of the attention in American diets).

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The condition is triggered by an intolerance to gluten, a protein found in wheat, barley and rye - and therefore a common ingredient in many processed foods.

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The protein is found in wheat and related grains that are food staples in large parts of the world.

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Coeliac disease is caused by gluten, a protein that is found in wheat, and other similar proteins that are found in rye, barley, and oats.

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The report describes wheat as the world's most important plant-derived protein and calorie source.

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Staple crops like wheat, soy bean, rice and potato -- things that would provide carbohydrates, protein and fat -- they're the final end point.

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