High levels of a cancer-causing heavy metal and arsenic have been discovered in a river and reservoir in the southern Guangxi Zhuang Autonomous Region.?

High levels of a cancer-causing heavy metal and arsenic have been discovered in the reservoir at Lalang Hydroelectric Dam on the Longjiang River, Guangxi Zhuang Autonomous Region. [File photo]

Despite efforts to dilute the pollution, carcinogenic cadmium still remained at three times permitted levels in the reservoir at Lalang Hydroelectric Dam on the Longjiang River on Thursday afternoon.

Local officials said cadmium levels of 0.0247 milligrams per liter were recorded.

But arsenic content has fallen to safe levels since the water was diluted, reported Xinhua.

"Test results show that dilution has worked and will continue," said government officials in Hechi City, which administers Yizhou City.

Authorities in Yizhou City were alerted on January 15 when fish kept in cages in the reservoir died.

Officials ordered dam staff to discharge large quantities of water to dilute contamination.

The authorities have warned residents not to drink water from the river and wells are being dug to ensure safe drinking water, Xinhua said.

The pollution came from a source outside the city and an investigation is under way, said officials. It will focus on chemical and manufacturing plants along the river.

The Ministry of Environmental Protection has organized a work team to visit Guangxi to conduct a probe.

Cadmium is a key component in battery production, coatings, electroplating and toys. Exposure can result in fever, pneumonia, kidney failure and cancer.