NANNING - Three workers trapped in a collapsed tunnel of a metro line under construction in the southern Chinese city of Nanning have been rescued on Wednesday evening.

The accident happened at around 3 p.m. in the capital city of Guangxi Zhuang Autonomous Region, when three workers were working in a tunnel section under Minzu Avenue, rescuers said.

A government official said the workers were there for a project to move two sewage pipelines to make way for a new metro line.

All the three workers sustained injuries and have been sent to hospital.

The cause of the accident is not immediately known.

Wednesday's accident marked the second in three days related to metro lines under construction. On Monday, five workers were killed and 18 others injured after a platform collapsed in a parking lot being built to support a metro line in Shanghai.