Water and environmental authorities in south China's Guangxi Zhuang autonomous region are working to control cadmium pollution in a local river, while ruling out the possibility that water sources for Hong Kong and Macao have been contaminated.

Cadmium pollutants may be double the restricted level in the downtown section of the Liujiang River in Liuzhou, Guangxi Zhuang autonomous region, but authorities are making efforts to contain the contamination within the required standard, said Xu Zhencheng, an expert with the task force handling the pollution emergency.

Xu is a deputy chief of the South China Environmental Science Institute under the Ministry of Environmental Protection.

The pollutants were detected in Liujiang Thursday afternoon, more than 10 days after industrial waste from a local mining company polluted Longjiang, a tributary upstream of Liujiang, according to the city's environmental protection bureau.

Flocculent has been dumped into a dam on the Longjiang River in order to promote flocculation of the pollutants. The chemicals can help suspended heavy metal particles aggregate, facilitating the dredging of the pollutants when they form a floc.

By 6 a.m. Saturday, the water supply for residents in Liuzhou was safe, and the city government has promised that all the supply from the water plant meets the required standard.

Meanwhile, the government has also begun looking for alternative water sources for emergency use.

No contamination has been spotted in the downstream Qianjiang, Xunjiang and Xijiang rivers, said Xu.

Xijiang is a trunk of the Pearl River, a major water source for Guangdong province and neighboring Hong Kong and Macao special administrative regions.

The 500 million cubic meters of water at the Honghua Hydropower Station on the Liujiang River is expected to substantially dilute the pollutants, and, therefore, cadmium will be contained within the restricted level in the waters downstream of the station, Xu said.

Cadmium is a carcinogenic chemical mostly used in industrial effluents.

The pollution has caused panic buying of bottled water in parts of Liuzhou, a city with a population of 3.7 million.

A supermarket salesperson in the city's downtown area said sales of bottled water had more than tripled in recent days.

"Some people bought ten cardboard boxes of bottled water at a time," the salesperson said, adding that the store has ample stock, and there is no immediate threat to supply despite the surge in demand.

The local market watchdog has moved to ensure that prices for bottled water remain stable and supplies are sufficient in case the pollution prompts panic buying.

Guangxi Jinhe Mining Co. Ltd. has been held responsible for the contamination.