Four people have received jail sentences ranging from two and a half to five years for selling and producing melamine-tainted dairy products in northwest China's Shaanxi Province, court authorities said Wednesday.

Zhang Wenxue, former manager of Lekang Dairy Co. Ltd in Weinan city, was sentenced to five years in jail and fined 500,000 yuan (76,200 U.S. dollars), the Linwei District Court said in a press release.

Two deputy managers of the dairy firm, Zhu Shuming in charge of production and Tong Tianhu in charge of marketing, were sentenced to four years and fined 250,000 yuan each, the statement said.

Ma Shuanglin, a local dairy dealer, received a two-and-a-half year jail term and was fined 150,000 yuan for selling tainted milk powder to the dairy firm, the document said.

The document stated that Ma received 20 tonnes of contaminated milk powder from a local dairy firm on mortgage in July and August of 2008.

In September 2009, Ma sold 16.55 tonnes of the milk powder to Lekang Dairy Co., for 15,000 yuan a tonne, at least 25 percent cheaper than the average market price, under an agreement with Zhang and Tong.

Zhang and Tong told Zhu to mix the shoddy milk powder in Lekang's products, even though Ma did not present a quality report to prove its safety, the court said.

Workers at Lekang's factory reported to Zhang that the milk powder was stale and had worms in it, but Zhang told them to remove worms and continue production.

Lekang sold 28 tonnes of the tainted dairy products to a food company in Guangdong Province for 436,700 yuan. The Guangdong firm then sold 25 tonnes to another food dealer in Fujian Province.

About 6 tonnes of the dairy tested positive for melamine in Fujian's Zhangzhou city early in 2010.

The distribution of melamine-laced milk products in 2008 killed at least six infants and sickened 300,000 children across the country.

Following the scandal, the remainders of the contaminated milk powder were sealed and required to be destroyed, but some were illegally used as raw materials on dairy production lines.