Menu Foods Income Fund, whose pet food has been blamed for at least 14 deaths of cats and dogs, does not know how a toxic substance got into its products but will continue to operate the plants where the food was produced, company officials said on Friday.
Earlier on Friday, New York State officials said aminopterin, an ingredient used in rat poison, had been found in samples of the Ontario company's wet cat food.
Executives of Menu told reporters in Toronto that they will begin testing all suspect raw materials, and that they consider the possibility of tampering to be "remote."
"Some raw material entered our supply chain that did not meet the quality that had been represented," Menu Foods President Paul Henderson told a news conference. "We've identified a correlation with a single ingredient and we've stopped using that ingredient."
Menu would not confirm or deny earlier reports that identified wheat gluten from China as the suspect ingredient.
"We'll systematically go through every ingredient and eliminate them as a possibility," said Dr. Richard Shields, Menu's executive vice president. "We don't believe our quality control was lax."
The two U.S. manufacturing plants where the tainted "cuts and gravy" style food came from are in Emporia, Kansas, and Pennsauken, New Jersey. Though Menu has yet to pinpoint the exact source of the contamination in the wet food's production, both locations continue to operate.
"We've performed tests at those facilities without issue," said Henderson. "It's business as usual."
Menu Foods recalled millions of pounds of wet pet food under various brand names a week ago. It is sticking with its initial cost estimate for the recall of C$30 million to C$40 million ($26 million to $35 million).
Asked about compensation for medical bills of sick pets, Henderson said "to the extent that we identify that the cause of any expenses incurred are related to the food, Menu will take responsibility for that."
Asked if Menu would admit to any negligence in the matter, Henderson replied with a flat "No."
He did, however, acknowledge that the death count of animals poisoned by Menu's products is "probably higher" than the reported 13 cats and one dog.
Menu is already the target of at least three lawsuits over the recall.
Units of Menu Foods rebounded 30.8 percent on the Toronto Stock Exchange on Friday, after taking a beating earlier this week. The price jumped C$1.20 to C$5.10 on volume of more than 1.5 million units.