Seven chemical plant executives in Guangxi Zhuang Autonomous Region have been detained for discharging industrial waste into a south China river, said local government on January 30, 2012.

The Longjiang River in Liuzhou in south China's Guangxi Zhuang Autonomous Region is polluted by cadmium.

According to local environment protection department, all seven worked in Guangxi, including Jinchengjiang Hongquan Lithopone Material Co Ltd in Hechi City. Their identities were not revealed.

Cadmium pollutants were first detected in Longjiang River, a tributary upstream of the Liujiang River, on January 15, when cadmium concentration near the Lalang reservoir was 80 times higher than the official limit of 0.005 milligrams per liter.

The pollution was contained Sunday after the local environment watchdog confirmed no new leaks were found at the upstream source of the contamination.

However, the cadmium concentration levels were still 25 times higher than the official limit, said local environment protection department. The pollutants were flowing downstream and were close to a major drinking water source for Liujiang, a city with 1.5 million permanent residents in the city proper.

Along 200 kilometers of the river, 20 surveillance stations have been set up and more than 210 surveillance workers are monitoring water quality.

Environmental protection workers have been adding neutralizers, made from dissolved aluminum chloride, at six locations along the river to dissolve the contaminants.

Cleanup work will be conducted in an area located 6 kilometers downstream from the Luodong hydropower station, where the pollutants were concentrated on Sunday night, as well as another location near the Sancha hydropower station.