China is investigating milk products produced by the Mengniu Dairy Group, one of the country’s largest dairies, and Dumex, a unit of France’s Groupe Danone SA, for adding an unapproved additive and melamine to their milk, AP reported citing state media. The Shanghai Municipal Bureau of Quality and Technical Supervision said Mengniu Dairy is being investigated by China’s quality watchdog for adding an unapproved protein additive, osteoblast milk protein, to one of its lines of milk. State media said investigations into Dumex were centered on whether the company produced infant formula contaminated with melamine, an industrial chemical used in the manufacture of plastics and fertilizer. Last year, at least six Chinese babies died and nearly 300,000 were sickened with kidney stones and other problems by milk tainted with melamine. The scandal was one of the worst food contamination crises to hit China. The current investigation into Dumex was triggered by overseas media reports last month that some four dozen babies suffered kidney-related illnesses after drinking the company’s milk. Dumex and Mengniu claim their products are safe.