China admitted Tuesday that two local companies had illegally exported contaminated wheat gluten and rice protein for pet food, which is believed to be the cause of about 4,000 animal deaths in the US. The US Food and Drug Administration has also received around 17,000 complaints of sick pets while investigations show that more contaminated products ended up in livestock feed that made its way to 6,000 hogs and 3.1 million chickens, Reuters reported. However, there is apparently little danger to people. China originally denied that melamine, a chemical used in plastics and fertilizer, had been added to the wheat gluten and rice protein. But in the admission, published by state media, the General Administration of Quality Supervision, Inspection and Quarantine said the situation arose because the companies were illegally trying "to meet the contractual demand for the amount of protein in the products".