Four people were trapped after a railway tunnel under construction collapsed on Monday in Pu'er City, southwest China's Yunnan Province, according to the information office of the Pu'er municipal government.

The construction project of Wanggang Mountain Tunnel, located in Mojiang County, is undertaken by China Railway 16th Bureau Group Co. Ltd.

Rescuers have opened ventilation holes and a food delivery channel, and contacted with the trapped people. The rescue work is continuing.