SHIJIAZHUANG, China -- Xue Jianzhong never posted a sign on his ground-floor shop, but somehow everyone knew what he was selling. Customers from all over this dairy farming region in the northeastern province of Hebei flocked to Xue's dusty street to buy special concoctions that he said would make milk more nutritious -- and more marketable.

Advertised as a "protein powder," the substance was sold in 44-pound bags and was tasteless, odorless and white, like talc. It wasn't cheap, about $1 a pound, but it could be mixed into inferior milk or even with specially treated water and the result would be a milklike liquid that would pass government quality tests.

It wasn't until September, when Xue was arrested in connection with the investigation into the poisoning of tens of thousands of babies across China, that it became clear his secret ingredient was a toxic industrial chemical called melamine.

Melamine can mimic protein in nutrition tests for milk and in products such as wheat gluten and chicken feed. But when ingested in large amounts, it can cause kidney stones or death in children and animals.

The problem is not just a domestic one. Melamine has surfaced in foods sold across Asia and, earlier, in pet food that poisoned animals in the United States, tainting China's reputation as the world's factory.

How the same substance that had killed pets and was officially banned in China as an additive in food just last year wound up in baby formula and so many other food products is a story of desperate farmers, complicit chemical companies, and government officials who looked the other way. All were part of a system that allowed the network of melamine dealers to thrive.

Farmers and companies involved in food and feed production said that the doctoring of their products was an open secret in the countryside but that the salesmen had told them it was harmless.

"Actually, every milk collection center bought a lot of melamine," said Wang, a 60-year-old farmer in the village of Yudi, in the Shijiazhuang area, who would not give her full name because she feared retribution. "Everybody did this."

China's melamine trade is run by a criminal syndicate that has relied on chemical companies and underground laboratories for its supply. The trade has been supported by a customer base so eager for the substance that for years it turned a blind eye to its potentially deadly effects. Traditionally used in the manufacture of plastics and leather, melamine has made its way into the food supply in a way that was never supposed to happen.

Initially covered up by officials afraid of losing their jobs and besmirching the Beijing Olympic Games,（这句话是核心） the melamine contamination scandal began with infant milk formula that killed at least four infants and sickened 54,000 babies. It soon spread to candy, instant coffee, yogurt, biscuits and other products made with Chinese milk, prompting bans or recalls in 16 countries.

In recent weeks the toxin has been discovered in eggs and in animal feed, sparking fears that tainted foods go well beyond dairy products and may include fish, shrimp, beef and poultry.

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问题越来越多了，奥运之后食品安全如雨后春笋一样扑面而来，牛奶、柑橘、鸡蛋、牛肉等等都开始出现问题，我们要说这些问题是奥运后才开始出现的么？当然不是，只是奥运之前，很多国家已经对我们的食品安全提出了质疑，由此我们开始了一场现代的掩耳盗铃，那就是强化媒体管制，大家可以回想一下，奥运期间从来听不到食品安全的问题，甚至听不到任何负面的报道，但是把耳朵堵起来就能解决问题么?我们已经看到了严重的后果，那就是中国信誉受到了严重损害，中国制造在金融危机中本就生存艰难，现在失去信誉如同雪上加霜，中国奶制品企业很可能在此次危机中全军覆没，这对于中国的损失不可估量。我们必须倡导，严惩肇事者、广开言路、完善制度、加强监管。我们不想听到诸如，出口的食品质量肯定没问题之类的解释言语，因为这不禁无法挽回食品安全的声誉，还损害了祖国人民的感情！