More than 80 workers were feared dead last night after being buried under rubble by a landslide which struck a Tibetan mine. About two million cubic metres of mud, rock and debris gave way and rolled down a slope in Lhasa's Maizhokunggar county, covering an area of three to four square kilometres, China Central Television (CCTV) reported. The disaster, triggered by natural forces, happened at 6am, according to Xinhua. A total of 83 workers were buried, of whom two were Tibetan and the rest Han Chinese, mostly migrants from the southwestern provinces of Yunnan , Guizhou and Sichuan . Pang Chunlei, a Tibetan police and rescue commander, told CCTV: "We rushed to the scene immediately and found the situation was serious." Over 1,000 rescuers and 200 large machines, 15 sniffer dogs and 15 life-detection machines were deployed at the site. However, Pang was not optimistic any survivors would be found. "The workers live in tents and have been buried by the landslide. We are digging but still haven't found anyone yet because the collapsed area is just too huge. It covers the entire mountain gully," Pang said. The site is at an altitude of 4,600 metres, and oxygen content is less than 50 per cent of what it is at sea level, which could further impede rescue work, CCTV reported. President Xi Jinping and Premier Li Keqiang issued an order for local governments to find out the exact number of missing workers and co-ordinate the rescue work. Copper, some gold and silver are mined at the facility, the largest investment project of the Tibet Huatailong Mining Development Company, a subsidiary of the China National Gold Group. The corporation was the first state enterprise to develop a mine in the Tibetan region, CCTV reported. Production began in 2010, according to Huatailong Mining's website.