NANNING - A southern Chinese city on Monday announced a plan to build an alternative drinking water source after a spill of toxic cadmium in a river threatened drinking water supplies for millions.

The city government in Liuzhou, Guangxi Zhuang autonomous region, said in a statement that it will build a reservoir on the Guchang River with a storage capacity of 100 million cubic meters.

The city now completely relies on the Liujiang River for tap water, and the reservoir on Guchang River will offer a second choice.

The reservoir is designed to help to meet the city's demand for two months in the summer and three months in the winter, the city government said.

Cadmium pollution was first detected in the Longjiang River on January 15 in Hechi, and it later spread to the downstream Liujiang River, threatening water security in Liuzhou, a city with 1.5 million permanent residents.

Days of cleanup efforts have managed to bring down the pollution levels near or within the official limit, the statement said. The contamination has killed many fish and triggered panic buying of bottled water.

Seven government officials in Hechi, including the city environmental protection chief, have been dismissed from their posts after the toxic spill.

The authorities in Hechi city Sunday said they will relocate all smelting plants within five years in response to the toxic spill of the cancer-causing cadmium.

Investigations found two factories, one producing a dye product called lithopone without a license, and the other a metallurgical chemical plant, were responsible for the incident. They had illegally discharged highly contaminated sewage.