Pet Food Poisoning Mystery May Be Solved

Returned cans of pet food fill a shopping car at Petco March 19, 2007 in Miami, Florida. At least 10 pets have died after eating from among 40 brands of food, including popular sellers like Iams, Eukanuba and Science Diet, produced by a Canadian company called Menu Foods. The company has issued a recall of 60 million cans and packages of moist dog and cat food that is believed to have cause kidney failure in the animals that died. (Photo by Joe Raedle/Getty Images)
The mystery of how two chemicals that are considered non-toxic poisoned so many pets may have been solved, CBS News correspondent Nancy Cordes reports.

The breakthrough was made at the University of Guelph in Ontario, Canada. A week ago, scientist Perry Martos mixed together a few drops of melamine and cyanuric acid, the two unauthorized chemicals found in tainted pet food.

In less than a second, they formed a mass of crystals nearly identical to crystals found in the kidneys of sickened animals.

"If you can imagine an instantaneous kidney stone — that's essentially the way I would perceive it," says Martos.

Dr. Kimberly May of the American Veterinary Medical Association says the discovery could end up saving the lives of animals that eat the tainted food, Cordes reports.

"It's very possible that the crystals that are formed may be dissolved by ... altering the medical treatment somehow, and that is being investigated," she said.

Meanwhile, the Chinese government reportedly has made one arrest in the contamination case. It's believed the chemicals were added deliberately as cheap substitute for real protein.

In Washington, the Senate voted unanimously Thursday to standardize the nutrition labels on pet food and to fine pet food makers who don't report problems right away.

These discoveries come as Menu Foods recalled yet another batch of its products. Menu Foods said the recall was due to possible cross-contamination between melamine-tainted products and other foods made in the same period.

The expansion includes cuts and gravy pet food, as well as other products that were not made with the contaminated wheat gluten supplied by ChemNutra Inc., but were manufactured during the period the chemical-laced gluten was used.

The company based its decision on study results that revealed cross-contamination, as well as one report from a customer.

The recall now includes additional pet food products in the United States, Canada and Europe. It also expands the date ranges of previously recalled products to match the period that melamine-tainted wheat gluten was used in manufacturing plants.

Menu estimates that the additional itemed added to the recall represent less than 5 percent of all products already recalled or withdrawn.

More than 100 brands of pet food have been recalled since March 16 because they were contaminated with melamine. An unknown number of dogs and cats have been sickened or died after eating chemical-laced pet food.

For a complete list of Menu's recalled products visit their Web site at Menu Foods.

Check the FDA Web site for the full list of recalled brands.