China?s investigation of the tainted milk powder that sickened hundreds of babies widened to its dairy-producing regions yesterday, as officials attempted to track down the source of melamine in the milk.One baby died and over400 developed kidney problems after drinking formula made from milk powder sold by Sanlu Group, one of China?s largest milk powder producers that is partly owned by New Zealand?s Fonterra Co-operative Group.Farmers or dealers supplying milk to Sanlu may have diluted it with water and then added melamine, a substance used in plastics, fertilizers and cleaning products, to make the milk?s protein level appear higher than it actually was. Teams traveled to Hebei, Guangdong, Heilongjiang and Inner Mongolia, the biggest dairy-producing regions, to reinforce local governments, ensure dairy inspections were fully carried out, and check milk powder already in circulation.

Sanlu admitted that its baby formula had been contaminated with melamine, which linked to deaths and illness of thousands of pets in the United States last year after it was added to pet food components exported from China. In 2004, at least 13 babies in the eastern province of Anhui died after drinking fake milk powder that investigators found had no nutritional value. The scandal prompted government efforts to strengthen monitoring of food safety.