WASHINGTON — A third company yesterday recalled pet foods made with an imported Chinese ingredient only recently found to have been contaminated by an industrial chemical.

The pet food ingredient, rice protein concentrate, is the second found in the U.S. to be contaminated by melamine. Previously, testing revealed that wheat gluten also had been contaminated.

Royal Canin USA said it was recalling some of its dry dog and cat foods made with tainted rice protein concentrate.

Also this week, the French company's South African unit recalled a range of dog and cat dry pet foods after they were found to contain a third ingredient, corn gluten, also contaminated with melamine. Those products were sold in South Africa and Namibia.

Petri Vogel from the South African Veterinary Association said 30 dogs had died across the country in the past two weeks after eating the contaminated food. She said the animals had died of renal failure.

Vogel said it was likely that there was a link between the contaminated products in the U.S. and South Africa.

The U.S. recalls began in March after the deaths of 16 pets. U.S. officials have not provided updated numbers of pet deaths or injuries due to the contaminated pet food.

Chinese authorities have told the FDA that the wheat gluten was an industrial product not meant for pet food, Stephen Sundlof, the FDA's chief veterinarian, said Thursday. Still, melamine can skew test results to make a product appear more protein-rich than it really is, he added. That raises the possibility the contamination was deliberate.