Menu Foods cannot explain toxin in its pet food

TORONTO (Reuters) - 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 product, company officials said on Friday.

Executives told reporters in Toronto that they will begin testing all suspect raw materials, and consider the possibility of tampering to be "remote".

Earlier in the day, New York State officials said aminopterin, an ingredient used in rat poison, was found in small samples of the Ontario company's wet cat food.

Menu Foods recalled millions of pounds of wet pet food under various brand names a week ago.