Six workers were killed and two others slightly injured after a collapse in a tunnel under construction in east China's Anhui Province early on Saturday, local authorities said.

The accident happened at about 12:53 a.m. in the tunnel that is being built for a highway bridge across the Yangtze River near Dongzhi County of Chizhou City, a county government spokesman said.

The injured workers are being treated at a local hospital, the spokesman said.

An investigation into the cause of accident is under way.