China is investigating the safety of milk products produced by one of the country's largest dairies and a unit of France's Groupe Danone SA, AP reported. Both companies insisted there were no problems. The Shanghai Municipal Bureau of Quality and Technical Supervision said on Thursday that the bureau was looking into "the quality and safety of Dumex milk powder" but did not give other details. The report said that investigations were centered around whether Dumex produced infant formula contaminated with melamine, which is used in the manufacture of plastic and fertilizer.