Sanlu was one of China 's leading dairy producers . Chinese investigators found melamine in nearly 70 milk products from more than 20 companies , according to then-quality control official Li Changjiang , who was forced to resign . Some Chinese dairy plants added melamine to milk products to boost protein levels . Ingesting melamine can lead to kidney stones , eye and skin irritation , experts say . Official : The government has said it will investigate the cause of the contamination
Sanlu was one of China 's leading dairy producers . Some Chinese dairy plants added melamine to milk products to boost protein levels . Ingesting melamine can lead to kidney stones , eye and skin irritation , experts say . Official : The government has said it will investigate the cause of the contamination