Four people were killed and another five injured on Sunday in a road crash in northwest China's Gansu Province, safety watchdog said. The accident happened around 3 p.m. when a car registered in Shaanxi Province crashed into a semi-trailer along a national road in the county of Qin'an, Xinhua quoted an official with the provincial work safety and supervision bureau as saying. Four passengers in the car died on the scene, with two others injured. The accident also injured three people who were working nearby, said the official. The injury conditions of the five are unknown. The cause of the accident is being investigated.