Washington ? A greater sensitivity of cats to a chemical found in plastics and pesticides could explain why they’ve died in larger numbers than have dogs after eating contaminated pet food, experts said Saturday.

The small number of confirmed reports of pet deaths bolstered by a far larger number of unconfirmed anecdotal reports suggests cats were more susceptible to poisoning by the chemical melamine that tainted the now recalled pet food, officials with the Food and Drug Administration and American Society for the Prevention of Cruelty to Animals said Saturday.

“I am concerned we have a situation where we have a sensitive species and it is the cat,” said Steven Hansen, a veterinary toxicologist and director of the ASPCA’s Animal Poison Control center in Urbana, Ill.

Testing by the FDA and Cornell University has found melamine in samples of recalled pet food as well as in crystal form in the urine and kidney tissue of dead cats. They’ve also found the chemical, in apparently raw form in concentrations as high as 6.6 percent, in wheat gluten used as an ingredient of the recalled cat and dog foods, said Stephen Sundlof, the FDA’s chief veterinarian.

“There was a sizable amount of melamine. You could see crystals in the wheat gluten,” Sundlof told The Associated Press.

Sundlof and others have not been able to explain why the chemical would have caused the kidney failure seen so far in the roughly 16 confirmed pet deaths, all but one in cats. There are anecdotal reports of hundreds more pet deaths.

“It has a very low toxicity, at least in rodents. The problem is, we don’t have information in cats, and that seems to be the most susceptible species,” Sundlof said of melamine. He also allowed that the tainted cat foods could have contained higher concentrations of melamine than the dog foods.

Nestle Purina PetCare Co. said Saturday it was recalling all sizes and varieties of its Alpo Prime Cuts in Gravy wet dog food with specific date codes. Purina said a limited amount of the food contained a contaminated wheat gluten from China.

Earlier this month, Menu Foods became the first pet food manufacturer to recall its products. It did so after cats began to fall sick and die during routine company taste tests of its wet-style pet foods, sold under nearly 100 store- and major-label brands across North America. Other than in the recalled products, melamine has not been found in other Menu Foods pet foods, the company said.

Melamine is used to make plastic kitchenware, glues, countertops, fabrics, fertilizers and flame retardants. It also is both a contaminant and byproduct of several pesticides, including cyromazine, according to the Environmental Protection Agency.