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, the city's environmental protection bureau said.

But test results published every two hours indicated that the pollution was not severe and no apparent harm had been done to the river's upper reaches, the city's major drinking water source, said Gan Jinglin, Liuzhou's environmental chief.

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

But 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.

Meanwhile, the city has opened sluices at four upstream hydrological stations, hoping to dilute the pollutants.

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.

Liuzhou has a population of 3.7 million.

Guangxi Jinhe Mining Co. Ltd. has been held responsible for discharging waste and therefore polluting the Longjiang River, a tributary upstream of the Liujiang River in Hechi on January 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.

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

Cadmium, a chemical that is mostly found in industrial effluents, is carcinogenic.