GUIYANG - The death toll of a bus-truck crash on an expressway in Guizhou Province Saturday morning has risen to four after a seriously injured person died in hospital, local authorities said.

The accident happened at 6:30 am when a long-distance coach overturned and caused the collision of another coach and a truck on a section of the Lanzhou-Haikou Expressway in Zunyi city, according to the city's fire department.

The more than 70 injured, including one critically, have been rushed to two local hospitals.

An initial investigation revealed that the Hainan-registered coach travelling to Chongqing overturned suddenly on the slippery expressway after downpours. Another coach behind it then slammed into a truck.

Two passengers of the overturned coach and the driver of another bus were killed at the scene, said the firefighters.

The expressway was temporarily closed, said the local traffic police.

A further probe into the cause of the accident is underway.