NANNING, May 13 -- Five construction workers have died after a staircase in a building they were working on collapsed on Tuesday morning in south China's Guangxi Zhuang Autonomous Region.

The accident happened in an under-construction building in Lingui County at 8:15 a.m. when seven workers were on-site. One worker was killed on the spot while four others died in hospital.

The two other workers were injured but are now in a stable condition and receiving treatment.

The cause of the accident is under investigation.