American officials now believe contaminated wheat gluten distributed by an unnamed U.S. company may have spread to dry pet food, despite assurances the problem was contained.

Hill's Pet Nutrition, a division of Colgate-Palmolive Co., recalled its Prescription Diet m/d Feline dry cat food on Friday.

The food included wheat gluten from the same supplier used by Menu Foods; however, Menu Foods is not affected by the latest recall because the company only manufactures wet pet food products.

Earlier Friday, the U.S. Food and Drug Administration said melamine, a product used as a fertilizer in Asia and in commercial plastic products in North America, had been identified in the wet pet food.

Along with Hills's Pet Nutrition's Prescription Diet m/d Feline dry cat food, here are the lists of the recalled Menu Foods products:

The Menu Foods recall information number is 1-866-895-2708 or 1-866-463-6738.

Animal advocates had called for the current recall -- which involves nearly 100 brands of "cuts and gravy'' style dog and cat food -- to expand to all dry foods.

Michael O'Sullivan, of the Humane Society of Canada, told CTV Newsnet the only safe option is to issue a complete recall.

"I think I'd rather err on the side of caution, and in our opinion it makes more sense to do a complete recall in order to protect those 13 million dogs and cats," O'Sullivan said during a news conference.

"Some people now believe dry food is what caused their animals' deaths, so the question has to be asked, shouldn't dry foods be added to the recall list," said Bruce Friedrich, PETA's vice-president of international grass roots campaigns.

"PETA is calling for precautionary dry food recall until it can be chemically tested and its safety assured."

Both Friedrich and O'Sullivan said more stringent mandatory requirements must be imposed on the pet food industry.

Contamination determined

Menu Foods says the source of contamination that sickened thousands of dogs and cats in Canada and the U.S. has been identified and removed, and its products are now entirely safe.

At a Toronto news conference Paul Henderson, president and CEO of Menu Foods, said the melamine was contained in wheat gluten provided by a new U.S. supplier that sources product from China.

He told reporters the supply is now safe.

"Quite simply, one supplier's product was adulterated in a manner that was not part of any known screening process for wheat gluten," Henderson said.

"The important point today is that the source of that adulteration had been identified and removed from our system."

He said the FDA's announcement earlier in the day supports the recall process used by Menu Foods and clears the company of wrongdoing.

Henderson also said the company will be providing compensation to customers for veterinary bills and said the investigation is ongoing.

"To the extent that there is a cause and relationship to the extent that the individuals suffered a loss as a result of consuming Menu Foods, yes Menu will take responsibility."

He also said there has been no further evidence that the pet food was contaminated with aminopterin, a rat poison and cancer drug.

The New York State Food Laboratory announced last week it had found aminopterin in the pet food.

The FDA probe found melamine in wheat gluten that was used as an ingredient in the pet food, in samples of the food itself, and in the urine and kidneys of some deceased cats.

FDA official Dr. Stephen Sundlof said there is little information in scientific literature about the effect of melamine on dogs or cats, so it's difficult to determine what would be a lethal dose.

Nor are officials certain melamine caused any deaths.

"Melamine is an ingredient that should not be in pet food at any level, however I want to make it very clear we are not fully yet certain that melamine is the causative agent of the illness and death of pets," Sundlof said.

The FDA had not identified aminopterin in the food or animals.

However, officials said melamine may not be the only "causative agent" in the 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 company's products.

It is unclear how many pets may have been poisoned by the apparently contaminated food, although anecdotal reports suggest hundreds, if not thousands, have died.

The FDA has received more than 8,000 complaints.

With files from CTV Toronto's Galit Solomon