URUMQI - Officials in a northwest China's desert oasis region have been banned from abusing their power to profit from the "jade rush," in which excessive mining has almost exhausted reserves of the precious stone.

The government of Hotan prefecture, Xinjiang Uygur autonomous region, has issued a circular that threatens officials with penalties including Party expulsion if caught profiting from the jade business. Under particular scrutiny will be their roles in excavation, protecting illegal jade diggers, investing in jade businesses, and bribery, local officials said on Monday.

Cash incentives ranging from 5,000 to 10,000 yuan ($793 to $1,586) are promised to informants in the crackdown, according to the circular.

The banks of the Yurungkax River in Hotan produce the world's finest jade - Hotan jade - and are renowned for their pure white nephrite variety of the stone.

Xinjiang produces some 250-300 tonnes of Hotan jade annually, 20 percent of which is pure white nephrite. A kg of the jade is usually priced over 100,000 yuan. But the prices have kept surging in recent years due to a steep decline in output.

Lured by get-rich-quick tales, jade hunters from all over the country swarm around the river during summer before it freezes over in autumn. And the rampant excavation is taking its toll on the environment.

The government has installed cameras and deployed inspectors at key road sections to keep tabs on heavy machinery in the area.