Four people were killed when the SUV they rode in crashed into a heavy-duty truck on an expressway in northwest China's Xinjiang Uygur Autonomous Region Monday, local authorities said.

The head-on crash happened at 2:05 a.m. on a newly-completed expressway linking Xinjiang's Aksu city with Wensu County.

Both vehicles caught fire after the collision, said the government of Aksu Prefecture, without identifying the victims.

The cause of the accident is under investigation.

The Aksu-Wensu expressway is an extension of the pivotal link between Aksu City and Kuqa County. It was completed in July and has not officially opened to traffic.