The Food and Drug Administration said today it found melamine in samples of the Menu Foods pet food involved in the original recall and in imported wheat gluten used as an ingredient in the company's wet-style products. Cornell University scientists also found melamine in the urine of sick cats, as well as in the kidney of one cat that died after eating some of the recalled food.

Meanwhile, Hill's Pet Nutrition recalled its Prescription Diet m/d Feline dry cat food. The food included wheat gluten from the same supplier that Menu Foods used. The recall didn't involve any other Prescription Diet or Science Diet products, said the company, a division of Colgate-Palmolive Co.

The FDA was working to rule out the possibility that the contaminated wheat gluten could have made it into any human food, but was not aware of any risk to people.

It wasn't immediately clear whether the melamine was the culprit in the deaths of more than a dozen cats and dogs and the illnesses of hundreds more, said Stephen F. Sundlof, director of the FDA's Center for Veterinary Medicine.

Wheat gluten, a source of vegetable protein, is also used in some human foods, but the FDA emphasized it had found no indication that the contaminated ingredient had been used in food for people.

The FDA said it would alert the public quickly if the melamine was found in any foods other than the recalled pet food.

Menu Foods recalled 60 million containers of cat and dog food earlier this month after animals died of kidney failure after eating the Canadian company's products. It is not clear how many pets may have been poisoned by the apparently contaminated food, although anecdotal reports suggest hundreds if not thousands have died. The FDA alone has received more than 8,000 complaints.

The new finding comes a week after scientists at the New York State Food Laboratory identified a rat poison and cancer drug called aminopterin as the likely culprit in the pet food. The FDA said it could not confirm that finding.

New York officials have detected melamine in the recalled food as well. Yet New York remained confident in its aminopterin finding, said Patrick Hooker, commissioner of the New York state Department of Agriculture and Markets. Hooker added that neither aminopterin nor melamine should be in pet food, but that it was unclear why the latter substance would be poisonous to the cats in which it was found.

"While we have no doubt that melamine is present in the recalled pet food, there is not enough known data on the mammalian toxicity levels of melamine to conclude it could cause illness and deaths in cats. With little existing data, many questions still remain as to the connection between the illnesses and what has caused them," Hooker said.

The recall involved nearly 100 brands of "cuts and gravy" style dog and cat food made by Menu Foods. The recall covered products carrying names of major brand-name and private-label products sold throughout North America.

Menu Foods used wheat gluten to thicken the gravy of its pet foods, FDA officials have said.

Menu Foods spokesman Sam Bornstein did not know whether company testing had found melamine in its products.