However, several of the companies recalling food contend in statements on their Web sites that American Nutrition added the rice protein concentrate to their products without their knowledge or approval.
"It appears that ANI had been adding the unauthorized rice protein concentrate to Harmony Farms products for some time and only told the company when the FDA was about to conclude that some of ANI's rice protein concentrate (supplied by Wilber-Ellis) was contaminated with melamine," said a statement on the Harmony Farms site.
Other companies making similar allegations are The Blue Buffalo Co., Natural Balance, Canine Caviar, Diamond Pet Foods and Mulligan Stew Pet Food.
The melamine in the food has been causing kidney failure in cats and dogs that have eaten the food. Melamine is used to produce plastic kitchenware and is used as a fertilizer in Asia.