SHANGHAI (AP) -- Three Shanghai dairy executives have been sentenced to jail after milk products their company made were found to be tainted with an industrial chemical at the center of China's milk safety scandal.

Shanghai Panda Dairy Co. was forced to close last year when unacceptably high levels of melamine, which can cause kidney stones or failure, were found in milk powder and condensed milk. Some Shanghai Panda products contained more than 34 milligrams of melamine per kilogram, well over the legal limit of 2.5 milligrams.

Fengxian District Court official Yang Xuelong confirmed Wednesday that the three executives were sentenced to jail terms of three to five years. He would not comment further.

In 2008, the discovery of widespread melamine contamination of milk, baby formula and other dairy products prompted an overhaul of China's entire dairy industry. At least six children died after drinking contaminated baby formula and more than 300,000 were sickened.

New cases appeared last year, some of it from old batches that weren't destroyed after the 2008 scandal, underscoring the difficulties China faces in improving food safety.

Melamine is used in making plastics, fertilizers and even concrete, but also can also fool tests checking the protein content of dairy products.

Despite a tough food safety law, Chinese authorities have had trouble regulating countless small enterprises and illegally run operations often blamed for introducing illegal chemicals and food additives.

The official Xinhua News Agency said the court found Shanghai Panda's company representative, Wang Yuechao, its general manager, Hong Qide, and deputy general manager, Che Dehua, responsible for making milk flavorings with melamine-tainted condensed milk.

The contaminated milk used by Shanghai Panda had been returned by a dealer, state media reports said. The company's contaminated products were tracked down and destroyed, and its business and food production licenses revoked.

China has punished nearly two dozen people blamed for making or selling tainted-milk products, including executing a dairy farmer and milk salesman.

Copyright 2010 The AP.