Story Highlights• Companies have issued alerts and recalled numerous varieties of pet food
• The chemical melamine, which can be toxic, has turned up during testing
• The problem was traced to wheat gluten obtained from a Chinese company
• The FDA has blocked further gluten imports from that company
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(CNN) -- Canadian pet food manufacturer Menu Foods has recalled numerous varieties of pet food made before March 6. Other companies have also issued alerts.
Federal testing of some of the cat and dog food and the wheat gluten used in their production turned up the chemical melamine, which can be toxic in high doses. (Check the full list of brands affected)
Earlier, the New York State Food Laboratory identified aminopterin, a cancer drug also used as rat poison, as the likely culprit in the pet food. But the U.S. Food and Drug Administration said it could not confirm that finding.
Menu Foods said the problem was traced to wheat gluten obtained from the Xuzhou Anying Biologic Technology Development Company in China. The FDA has blocked further gluten imports from the company.
The Chinese company termed the reports of chemicals in its product "rumors," but says it is cooperating with the FDA investigation. (Read the FDA's latest information on the pet food recall)
Gluten brings elasticity and chewiness to baked products.
Menu Foods makes only "wet" pet food, such as "chunks and gravy" style varieties.
Nestle Purina also has recalled its Alpo Prime Cuts in Gravy dog food that was supplied with some of the suspect wheat gluten.
The only dry product affected is Prescription Diet dry cat food made by Hill's Pet Nutrition of Topeka, Kansas. Hill's obtained wheat gluten from the same supplier as Menu Foods.
Click on the links below for details from the manufacturers of brands, flavors and production batches affected by the recall.
The FDA said pet owners should consult a veterinarian if their animals show signs of loss of appetite, lethargy or vomiting.