At least seven people were killed and 12 others were injured and hospitalized in a road accident involving nine vehicles on the Ya'an-Xichang Expressway in southwest China's Sichuan Province on Friday, according to police. 

The accident occurred on the section between Xichang to Chengdu, both in Sichuan, at 16:30 local time. 

An investigation into the cause of the accident is underway.