VIDEO: Fifty-One Believed Dead In China Bus Crash

The long-distance bus tumbled into a 100-metre (300-foot) deep valley in Nanjiang County.

Fifty-one people are believed to have been killed when a bus in which they were travelling plunged into a valley in southwest China's mountainous Sichuan Province on Saturday, the official Xinhua news agency reported.

The long-distance bus tumbled into a 100-metre (300-foot) deep valley in Nanjiang County. People nearby said they heard an explosion and saw thick smoke coming from the crash site.

Rescue activities were under way, but authorities are holding out little hope of finding survivors, Xinhua quoted a county official as saying.