More than 80 workers were buried when a huge landslide came crashing down a mountainside in Tibet on Friday, Chinese state-run media said.
A vast three-kilometre-long section of land, with a volume of two million cubic metres, slid down a slope and buried 83 miners in Maizhokunggar county, east of the Tibetan capital Lhasa, the official Xinhua news agency said.
A total of 1,000 police, firefighters and doctors were sent to the disaster site, at an altitude of 4,600 metres, the agency said, with 200 vehicles and 15 dogs, and sets of life-detecting equipment.
State broadcaster CCTV quoted a member of the Chinese People's Armed Police on the scene as saying that "the situation looks serious, the collapsed area is three or four square kilometres".
Rescuers have so-far found no signs of the trapped workers, the policeman added.
The workers were from China National Gold Group Corporation, a mining firm.
Almost all of them were Han Chinese, the national ethnic majority, with only two of them ethnic Tibetans, Xinhua added. Most were migrant workers from the provinces of Yunnan, Guizhou and Sichuan.
China's new president Xi Jinping, who is currently visiting the Republic of Congo in Africa, and new premier Li Keqiang had ordered "top efforts" to rescue the victims, Xinhua added.
"Xi and Li have told local authorities to spare no efforts to rescue the buried and prevent secondary disasters," it said.
A worker at a hospital in the county reached by AFP late on Friday said it had not yet received any casualties but staff were "making preparations".
A female member of staff who answered the phone at the county government office said she was not clear about the situation and hung up.
The Lhasa city government and China National Gold Group Corporation did not immediately answer calls late Friday.
The landslide struck at about 6am local time, but Xinhua's first news reports about it ran more than 15 hours later.
Mountainous regions of Tibet are prone to landslides, which can be exacerbated by heavy mining activity.
Han Chinese have been increasingly moving into historically Tibetan areas, and many Tibetans in China say their culture is being eroded.
Beijing rejects criticism of its rule, pointing to huge ongoing investment it says has brought modernisation and better standards of living to Tibet.