The people caught in the slide are workers of a subsidiary of the China National Gold Group Corp., the state-run Xinhua News Agency reported.
The slide buried a workers' camp, along with motor vehicles, Xinhua said.
Officials said rugged terrain made rescue efforts difficult.
Xinhua said more than 1,000 rescue workers, with 200 vehicles, 15 dogs and 15 life-detection machines, were at the site, which is at an altitude of 4,600 meters (15,088 feet).
The affected area of the landslide is 3 kilometers long (1.86 miles) with about 2 million cubic meters (2,616,000 cubic yards) of mud, rocks and debris in Maizhoukunggar County, east of the regional capital of Lhasa, the regional government's publicity department said.