A tour bus plunged into a Tibetan valley on Saturday after hitting two vehicles, killing 44 people and injuring 11, Xinhua News Agency reported.

"The 55-seat bus carrying 50 people fell off a 10-meter-plus cliff after crashing into a sport utility vehicle and a pickup truck," the report said, citing the regional government.

Five people were in the truck and SUV involved in the accident, which occurred at around 4:25 pm in Nyemo county, west of the capital, Lhasa, in the Tibet autonomous region.

The bus passengers were mainly tourists from several eastern regions in China. The injured were being treated at hospitals in Lhasa and did not have life-threatening injuries, Xinhua said.

Police have detained the managers of a travel agency and vehicle tour company, who are being held responsible for the crash.

"The regional government has held an emergency meeting, ordering a general overhaul of road safety and travel safety across the region to avoid similar fatal accidents," the report said.

Fatal road accidents are a serious problem in China, particularly involving the country's often overcrowded long-distance buses.

The Ministry of Transport says the number of road deaths in China fell from 104,000 in 2003 to 60,000 in 2012, or from about 300 fatalities a day to fewer than 200.

In July, 43 people died when a van carrying flammable liquid hit a bus on a motorway in central China.

In August 2012, at least 36 people died when a double-decker sleeper bus slammed into the rear of a methanol tanker and burst into flames in northern China.