BEIJING - Authorities say 21 people were killed when a bus ran through a roadside fence and plunged into a lake in a southwestern Chinese city.

Surveillance video posted by state broadcaster CCTV on its social media account show the bus suddenly race across six lanes of traffic and through a fence.

The Anshun city government said 15 people were rescued and sent to hospitals with injuries.

It did not give a cause of the accident.

The passengers included high school students taking nationwide university entrance exams that began Tuesday.