The death toll has risen to 13 from a traffic collision on a highway in east China's Shandong Province after five severely injured died in hospital, local authorities said Tuesday.

A truck collided with a mini-bus at about 7:10 p.m. Monday on a highway near the border of Huantai County and Boxing County, instantly killing eight people in the mini-bus and injuring 13 others, seven severely, a spokesman with the Shandong provincial government said.

The injured were rushed to two hospitals in Huantai, but five of the severely injured died Tuesday, the spokesman said.

Police are still investigating the cause of the accident, he added.