The deluge shortly after midnight swallowed 15 employee dormitories and three residential houses in Shangluo, in the northern province of Shaanxi, the city government said in a statement on Wednesday.
Around 40 people were missing, it said, adding that police, firefighters, mining rescuers and medical staff had been sent to the site and residents in the area evacuated.
Local officials say at least four people have been rescued, and that police, firefighters, mining rescuers and paramedics have been dispatched to the area.
Xinhua says the landslide occurred at the Wuzhou Mining Company. The company mines vanadium, which is used in steel alloys.