According to the same AP story, New York officials are sticking by their guns:
New York officials stuck to their aminopterin finding and pointed out that it was unlikely that melamine could have poisoned any of the animals thought to have died after eating the contaminated pet food. Melamine is used to make plastic kitchen ware and is used as a fertilizer in Asia.
An FDA official allowed that it wasn't immediately clear whether the melamine was the culprit.
So which foreign substance is killing thousands of cats and dogs? Could it be a combination of both? And in practical terms, does it make you feel any better about Menu Foods, knowing that both a rat poison and a plastics chemical have been found in their food?
I guess this news doesn't bother the dozens of pet food companies who continue to use Menu Foods as their manufacturer.