sentences:  Finally, China's Foreign Ministry says that it has banned the use of melamine in food products, admitting that products containing melamine had cleared customs while continuing to dispute the role of melamine in causing pet deaths.China also vowed to cooperate with U.S. investigators to find the "real cause" of pet deaths.Natural Balance Inc. issues another voluntary recall, recalling three of their varieties of dog food and one variety of cat food, and Canine Caviar issued a voluntary recall of 3 varieties of pet food.