NANNING, Feb. 27(Xinhuanet)-- One worker died and four were injured when a steel roof frame collapsed at a construction site Sunday afternoon in south China's Guangxi Zhuang Autonomous Region,local workplace safety officials confirmed.

Ten workers were hoisting a steel roof in Wucunling of Nanning,capital of the autonomous region, at 3:00 p.m. when the roof framesuddenly fell.

The one worker was killed on the spot. The four injured were rushed to a local hospital and two of them were in critical condition at the press time.

The surviving workers said most of the workers were not wearingsafety helmets because their employer had not provided any.

Investigation into the cause of the accident is underway.