Chinese government is investigating reports that a brand of powdered milk caused infant girls to grow breasts. It is being alleged that hormone-tainted milk from Synutra International caused several cases of premature puberty in Hubei province. The Chinese firm, whose shares fell by up to 35% on the news, strongly denies its products were tainted. Food safety problems involving milk powder and other products have alarmed Chinese consumers in recent years. Two years ago, the chemical compound melamine was found in milk products made by 22 Chinese firms. Hundreds of thousands of children were poisoned and six died.