Jade prospectors are putting one of China's rivers in danger and might soon exhaust supplies of the precious stone.

About 200,000 people are sifting the Yurungkax River in Xianjiang for Hotan jade - which costs up to $120 (£63) a gramme - state media reports have said.

In addition to the prospectors, around 2,000 mechanical diggers are sifting through the river bed for the gemstone.

Experts say the search is destructing the river bed and its biological system leading to serious soil erosion.

"The river bed, which is hundreds of millions of years old, is undergoing unprecedented degradation," said Wang Shiqi, a gemstones specialist at Beijing University.

"If the mass hunting continues like this, the river's Hotan jade resources will disappear in five to six years," he added.