One bus hit the rear of another bus shortly after noon in Guizhou province, and both vehicles fell about 500 feet, the Xinhua News Agency reported.

Police were investigating the cause of the accident. The exact number of passengers traveling on the buses wasn't immediately known, the report said.

China's roads are among the world's deadliest.

Last year, traffic accidents killed 104,372 people in China, according to government figures. Most accidents are caused by unsafe roads.