Residues from a local lead-zinc mine polluted a major river in central China's Hunan Province on Thursday night, cutting water supplies for more than a day in a riverside city and a downstream county with a combined population of 200,000, local authorities confirmed on Saturday.

About 30,000 cubic meters of lead-zinc residue were washed into the Zijiang River after the culvert under the tailings dam at the privately-run Zhongtai Mining Corp. collapsed on Thursday night in Lengshuijiang city, said Xie Li, an official with the Hunan provincial environment watchdog.

The dam was one of the four built to dam tailings in Lengshuijiang, a major industrial base in Hunan Province.

Xie said the accident caused no casualties but affected water supplies in Lengshuijiang city and Xinhua county in the lower reaches of the river.

Water supplies were suspended between 2:00 a.m. and 7:00 p.m. on Friday in Lengshuijiang. In Xinhua county, supplies were suspended for 22 hours until Saturday morning, said Su Guoyou, a spokesman with the Lengshuijiang city government.

By Friday night, rescuers had stopped the tailings from flowing into the river and built a new dam about one kilometer from the collapsed tailings dam.

The content of lead, zinc, cadmium, arsenic and chemical oxygen demand (COD) in the river water had turned normal by Friday morning, the local environment watchdog said after lab work.

Lengshuijiang city suffered a water crisis in 2005, when a fertiliser maker accidentally spilled more than 100 cubic meters of ammonia nitrate into the Zijiang river. Water supplies were suspended for 12 hours.

Zijiang is one of the major tributaries of the Yangtze, China's longest waterway.