Chinese police have detained three people in the northwestern Shaanxi Province over suspected tainted milk powder sales, before the products reach retail stores.

Liu Ping, general manager of Shaanxi Jinqiao Diary Company, and two of its employees Miao Wenjun and Lu Xiaoqiang were detained on Dec. 2 for the suspected crime of producing and selling toxic food, the provincial public security department announced Thursday.

They allegedly sold 5.25 tonnes of melamine-laced milk powder to Nanning Yueqian Food Additive Company in the southern Guangxi Zhuang Autonomous Region in September, said Xu Qiang, deputy head of the provincial public security department.

The food additive company discovered in early November in a detection that 5 tonnes of the milk power contained the industrial chemical melamine, which can cause kidney stones and kidney failure.

The Shaanxi Quality and Technical Supervison Bureau later confirmed in an examination that 11 of the 200 sacks of the milk powder had excessive melamine.

All of the tainted milk powder were confiscated on Nov. 18 and none of them was brought into the market, said Xu.

A melamine scandal over the tainted milk powder which broke in September last year was found to have caused the deaths of at least six children and sickened more than 300,000 others in China.