Three people were killed and four others were injured from a carbon monoxide leakage at a cement factory in southwest China's Yunnan Province on Monday.

Three of the injured remained stable, however, the fourth one is still in a critical condition, according to a local official with the work safety supervision administration of the Dehong Dai and Jingpo Autonomous Prefecture where the factory is located. The official only gave his surname as Zhao.

The accident happened on Monday morning at the Aohuan Cement Factory when two workers were conducting a routine safety examination for an elevator in a pit.

The two workers were accidentally poisoned from carbon monoxide leakage. Several workers nearby tried to help, but fell down as well.

Rescuers found two died at the site and another died later on the way to hospital.

Investigation into the cause of the accident is underway.

(Xinhua News Agency November 14, 2006)