The bus with 54 passengers on board fell 164 feet (50 meters) into a valley in Yangquan city Friday afternoon and 10 passengers were killed immediately, the official --inhua News Agency said. Three others died on the way to a hospital, and doctors were treating 41 injured passengers, it said.

Three of the injured were in critical condition and six others were seriously wounded, --inhua said.

The bus was en route from Hebei province to Shanxi's capital, Taiyuan. It had been rented by a health-care products company in Taiyuan to ferry customers to Hebei as a reward for using its products, --inhua said.

A Yangquan traffic police official confirmed the accident, but said 40 passengers had been hospitalized. The woman, who like many Chinese officials would give only her surname, Wang, said the cause of the accident was under investigation.

Zhang Yonghong, a Yangquan traffic police officer, told --inhua that it was drizzling when the accident happened and that the road was slippery.

Bus crashes are common in China, and are frequently caused by drivers who are speeding or who are sleepy, or are driving overloaded, poorly maintained vehicles.