A vehicle plunged into a cliff in southwest China's Sichuan Province Friday, killing five power maintenance workers and injuring eight others, local authorities said Saturday.

The accident happened at about 6:20 p.m. Friday on a narrow mountain road near Leshan City, when the 13 workers were traveling back home after completing a power line repair mission, said a spokesman with the Sichuan Provincial Electric Power Company.

The spokesman did not specify the type of the vehicle.

Heavy rain has made the mountain road very muddy and slippery, which was believed to have caused the vehicle to veer off the road, the spokesman said.

The eight injured workers have been hospitalized and were described as in stable condition.

Local police are investigating the accident, he added.