Five workers died and six were injured early Sunday when a huge rock fell from the ceiling of a tunnel under construction in central China's Hubei Province, local authorities said Tuesday.

The accident occurred in the Yunxian County, in Shiyan City, when more than 20 people were working in the tunnel that is being built as a part of an expressway, a spokesman with Shiyan Municipal Work Safety Administration said.

Five workers died instantly when the 7-meter-long, 3-meter-widestone unexpectedly fell, the spokesman said.

Two of the injured were seriously hurt, he said.

"They are being treated at a hospital in Shiyan, and all are in a stable condition," he said.

Local work safety authorities are investigating the cause of the accident, he added.

(Xinhua News Agency November 24, 2009)