WASHINGTON -- As many as one in six animals died in tests of dog and cat food that is part of a major recall.

Recall: Dog Products | Cat Products

Canadian manufacturer Menu Foods conducted the tests after fielding complaints that the products were killing pets around the country.

The government says Menu Foods tested suspect dog and cat food on as many as 50 animals after it learned of the problems -- weeks before the company announced its major recall of the affected food. Seven test animals died.

Menu Foods told the U.S. Food and Drug Administration that it received the first complaints of kidney failure and deaths among cats and dogs on Feb. 20.

During the tests, the company fed its product to 40 to 50 dogs and cats. Seven animals died. The mix of species was not immediately known.

The FDA said wheat gluten is the likely source of contamination that sparked a recall last Friday of 60 million cans and pouches of the suspect food, although the agency says its investigators are looking at other ingredients, too.

Wheat gluten, a protein source, is commonly used as filler.

Menu Foods said the products were made with wheat gluten from a new supplier. That supplier has been replaced.

The recall involves dozens of brands made by Menu Foods. The company said an undetermined number of cats and dogs have suffered kidney failure after eating the food and about 10 have died.

The recall includes "cuts and gravy" style dog and cat food produced at Menu Foods' facility in Emporia, Kan., between Dec. 3, 2006, and March 6, 2007.

The pet food is widely sold throughout North America under 51 dog-food brands and 40 cat-food labels, including Iams, Nutro and Eukanuba. The products are distributed by major retailers such as Wal-Mart, Kroger and Safeway.

A complete list of the recalled products along with product codes, descriptions and production dates is available from the Menu Foods Web site at menufoods.com.

Two other pet food companies -- Nestle Purina and Hill's Pet Nutrition -- are voluntarily recalling some of their products that are made by Menu Foods.

Officials are warning pet owners to immediately stop feeding the contaminated foods to their pets and said owners should see their pets' veterinarians if they develop signs of kidney failure, including loss of appetite, vomiting or lethargy.

Meanwhile, the recall has animal owners worried and scrambling to find substitutes.

Paul Castronovo, who is the weekday morning radio host on 105.9 F.M. in Miami, said his cat is in renal failure and it could be from the food, reported WPLG-TV in Miami

"Sunday morning we woke up and the cat couldn't move or hold its head up," Castronovo said. "We said, 'Well, let's take her to the emergency room.' At that point, I grabbed the newspaper and I noticed the headline that dogs and cat food recall. We both panicked and looked it up and it made me sick to my stomach. I saw that we served her Iams. It was the exact lot number. She's in complete renal failure."

A New Jersey woman became concerned when the four types of Iams products she buys for her cat, Smokey, had vanished from shelves. She said Smokey is very sick and hasn't been eating for days.

In Nebraska, another woman said she sometimes feeds her five cats packets of sliced meat and gravy sold by one of the brands affected. She said her cat, Boots, seems to have lost its appetite in the past few days.