Six workers were killed and another injured when boulders came hurtling down a slope in a mountainous region north of Shennongjia primitive forest zone, in central China's Hubei Province, local sources said Sunday.

The tragedy occurred in Fangxian, a mountainous county in northwestern Hubei, at about 2 p.m. on Saturday when nine workers were on their way to a hydroelectric plant construction site, said Guo Guanglin, deputy head of the Fangxian County Government office.

A big rock came crashing down just as the workers reached the foot of a mountain near Sanliping Village, killing three of the nine workers instantly and injuring four others. Only two of them escaped unhurt.

Three of the four injured died later in the local hospital, according to Guo.

The cause of the accident is under investigation.

Fangxian, which falls under the jurisdiction of Shiyan City, is about 600 km from Wuhan, the provincial capital of Hubei.

(Xinhua News Agecny October 8, 2006)