XI'AN - Two vehicles collided on a highway in Northwest China's Shaanxi province on Monday, leaving four people dead and another person injured, local authorities said.

The accident happened at 11:42 am on the Xi'an-Zhen'an section of the Baotou-Maoming Expressway, according to firefighters from Zhen'an county.

An initial investigation showed that a sports utility vehicle rear-ended a truck after the latter stopped suddenly near a tunnel entrance due to a flat tire.

Four people were pronounced dead at the scene. One injured person has been taken to a local hospital.

A further investigation into the cause of the accident is under way.