At least 40 people have died after a packed passenger bus plunged from the road into a rocky ravine in southwestern Pakistan early Friday.The crash killed 40 people and injured eight others, officials said.The bus went out of control and fell into the ravine in Dana Sar, a remote area near the border of Balochistan and Khyber Pakhtunkhwa provinces, Shahid Rind, a spokesperson for the Balochistan government, said.Rind said the bus was carrying not only its own passengers but also passengers from another bus that had broken down, leaving the vehicle overcrowded.In a statement, Balochistan Chief Minister Sarfraz Bugti expressed grief over the loss of life and ordered authorities to ensure the injured receive the best possible medical treatment.Rind said rescuers were working to identify those killed and treat the injured.Dana Sar mapped:Road accidents are common in Pakistan because of poor road conditions, inadequate enforcement of traffic laws and unsafe driving practices, particularly in mountainous areas.In May, a minibus rammed into a bus parked along a motorway in northwest Pakistan, killing 17 people and injuring five others.