LANZHOU, Oct. 12 (Xinhua) -- Five people were killed and another three were injured when an ambulance overturned in northwest China's Gansu Province on Sunday morning, local authorities said.

The accident happened at about 7 a.m. in Yumen City when an ambulance overturned and rolled off the highway, according to local traffic police.

The ambulance, with eight people on board, including a critically ill patient and relatives, was heading to central China's Henan Province from Urumqi, capital of northwest China's Xinjiang Uygur Autonomous Region.

The cause of the accident is being investigated.