State media says 15 people have died after a bus plunged into a ravine in central China. The official Xinhua News Agency said Friday 20 people were injured after the bus carrying 35 veered off a mountain road in Henan province. Twelve suffered serious injuries, including an 8-year old boy; five people were classified as in critical condition. The cause of the accident in Mianchi county is still being investigated. Road accidents are common in China because of overloaded and unsafe vehicles, poor road conditions and bad driving habits.