Pet Food Poisoning

May have been intentional.

Food and Drug Administration investigators say the Chinese companies may have spiked products with the chemical melamine so that they would appear, in tests, to have more value as protein products.

Officials now suspect this possibility because a second ingredient from China, rice protein concentrate, has tested positive for melamine. So has corn gluten shipped to South Africa.

Thanks to The Ministry of Minor Perfidy for the pointer (in the comments).