A total of four workers were killed and seven others injured after a cave-in inside a railway tunnel under construction early on Friday in northwest China's Qinghai Province.

The accident occurred at 12:15 a.m. in the Ketu Tunnel, in the Tibetan Autonomous Prefecture of Haibei, and buried 11 workers, the 12th Bureau of China Railway Construction Corporation (CRCC) said.

Rescuers pulled the trapped workers out, and found four had died in the collapse.

Two of the seven injured were in critical condition and were hospitalized in the provincial capital Xining.

The tunnel under construction belongs to the double track line of the Xining-Golmud Railway, which is a part of the Qinghai-Tibet Railway.

The line's operator, the Qinghai-Tibet Railway Corporation and the Qinghai Safety Supervision Bureau have begun a probe into the accident.

(Xinhua News Agency August 29, 2008)