Tin mines in the Hechi city area of Guangxi province, China, remain closed as the authorities investigate cadium poisoning of the Longjiang River. Last week ten people from two local zinc smelters were arrested, Metal Bulletin reported.

One of the plants, Guangxi Jinhe Mining, was discovered discharging smelting waste into the river. Jinhe’s chairman, vice general manager and environmental protection department head were amongst those arrested. Jinhe has refined zinc capacity of 60,000 tpy and also produces some 200 tpy of tin as well as other by-products. The other company, Jinchengjiang Hongquan Lithopone, was found emptying cadmium-containing waste water into the river in mid-January.

Guangxi accounted for 19% of China’s reported tin-in-concentrate production in 2011, with mining activity in the province largely concentrated in Nandan county, near Hechi. Mines operated by the province’s largest tin producer, China Tin, plus a number of smaller mines and smelters have now been shut for a month, with no indication yet from the authorities as to when they can re-start.