BEIJING -- Five people were killed and 12 others remained trapped after a landslide in northwestern China, state media said Tuesday.

The landslide shortly before 7 a.m. buried 33 people in Nanhe township of Longnan city in Gansu province, according to the official Xinhua News Agency.

The cause was unclear. Photos and video posted online by state broadcaster CCTV showed three excavators and rescuers on mounds of earth in an otherwise heavily wooded green area. The sky appeared sunny and clear.

Authorities relocated residents while rescue operations were underway.