LIUZHOU, Guangxi - Cadmium pollution caused by a mining firm has been found downstream of a tainted South China river, prompting local authorities to monitor drinking water safety more closely.

Cadmium pollutants were detected in the Liujiang River in Liuzhou, Guangxi Zhuang autonomous region on Thursday afternoon, more than 10 days after industrial waste from a local mining company polluted Longjiang, a tributary upstream of the Liujiang River, the city's environmental protection bureau said.

Cadmium is a carcinogenic chemical mostly used in industrial effluents.

Armed police dump bags of alkali into water to dissolve the contamination at the Nuomitan waterpower plant in Liucheng county of Liuzhou city, Guangxi Zhuang autonomous region, Jan 27, 2012. [Photo/Xinhua]

At Nuomitan Dam, armed police in chemical protective suits rushed to dump flocculants in the water - chemicals that will promote flocculation by cuasing suspended heavy metal particles to aggregate and form a floc.

The dam sits on Longjiang and only some 60 kilometers away from the city of Liuzhou with a population of 3.7 million. The levels of cadmium at the dam was five times above the standards.

But so far, water quality tests, conducted every two hours, showed that the drinking water source at the downstream of the dam had not been contaminated, said Gan Jinglin, Liuzhou's environmental chief.

"The water is still up to national standards and is safe for drinking," said Gan.

Local authorities have warned citizens not to fetch water from the polluted sections of the river. The government has begun looking for alternative water sources, fearing the pollution belt may spread further.

But panic buying of bottled water has began in parts of Liuzhou.

A super market salesperson in the city's downtown area said sales of bottled water grew more than three times in recent days.

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

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 discharging waste and therefore polluting the Longjiang River in Hechi City on Jan 15.

In Hechi, the pollution killed many fish and prompted panic buying of bottled water over the last week. Local fire authorities had put hundreds of tonnes neutralizers, made from dissolved aluminum chloride, into the Longjiang River to dissolve the contamination.

A local fisherman fetches drinking water from government-protected reach of the Longjiang River in Liuzhou city, Guangxi Zhuang autonomous region, Jan 27, 2012. [Photo/Xinhua]

The cadmium level has been declining in the Longjiang River since Thursday, the local government said.

Yet, as of Friday, more than 220 peasant farmers in two villages near the Longjiang River in Yizhou, a county-level city in Hechi, had relied on government-rationed water for nearly 10 days, as their well water remained unsafe for drinking.

The local government said 9.4 tonnes of water, in 520 barrels, had been delivered to the villagers since January 18, and another 2,000 tonnes is in storage.

Wang Jinhui, 53, said he used to fetch river water for cooking, drinking and bathing. After the pollution, his family of four were told to use the clean barreled water for safety reasons. "Each family gets two barrels a day. You can ask for more if you have guests."