The U.S. Food and Drug Administration is now looking into possible contamination of food consumed by humans. FDA officials said they would inspect imports of six grain products used for traces of melamine, a chemical thought to have killed and sickened cats and dogs. Melamine, which is used in plastics and fertilizer, has already been found in wheat gluten and rice protein imported from China for use in some pet foods, triggering a recall of more than 100 brands.