WASHINGTON - Pet food contaminated with an industrial chemical may have sickened or killed 39,000 cats and dogs across the United States, based on an extrapolation from data released Monday by one of the largest chains of veterinary U.S. hospitals.

Banfield, The Pet Hospital, said an analysis of its database, compiled from records collected by its more than 615 veterinary hospitals, suggests three out of every 10,000 cats and dogs that ate the pet food contaminated with melamine developed kidney failure. There are an estimated 60 million dogs and 70 million cats in the United States, the American Veterinary Medical Association said.

The hospital chain saw one million dogs and cats during the three months when the more than 100 brands of now-recalled contaminated pet food were sold. It saw 284 extra cases of kidney failure among cats during that period, or a roughly 30 percent increase, when compared with background rates.

"It has meaning, when you see a peak like that,'' said veterinarian Hugh Lewis, who oversees the mining of Banfield's database to do clinical studies.

"We see so many pets here and it coincided with the recall period.''

The chain continues to share its data with the U.S. Food and Drug Administration.

FDA officials previously have said the database compiled by the huge veterinary practice would probably provide the most authoritative picture of the harm done by the tainted cat and dog food.

From its findings, Banfield officials calculated an incidence rate of .03 per cent for pets, although there was no discernible uptick among dogs. That suggests the contamination was overwhelming toxic to cats, Lewis said. That is in line with what other experts have said previously.

At least six pet food companies have recalled products made with imported Chinese wheat gluten tainted with the chemical. The recall involved about one per cent of the overall U.S. pet food supply.

Last month, Ontario-based Menu Foods recalled 60 million cans and pouches of its "cuts and gravy'' style food, sold under 95 different brand names, for fear of contamination after it received reports of kidney failure and even death among dogs and cats.

While the company has agreed to reimburse customers for veterinary bills, it is still facing at least eight lawsuits, the most recent of which was filed Thursday by three Idaho residents.

Measuring the tainted food's impact on animal health has proved an elusive goal. Previous estimates have ranged from the FDA's admittedly low tally of roughly 16 confirmed deaths, to the more than 3,000 unconfirmed cases logged by one website.