In China, six persons were killed on Wednesday in a poisonous gas leak at a tunnel construction site in southwestern Yunnan Province. <br/><br/>Sources said, the accident happened in a tunnel along a pivotal railway line that will link the cities of Lincang and Dali. <br/><br/>State-run news agency Xinhua reported that the sulfureted hydrogen leak was accompanied by an outpouring of water and sludge inside the tunnel. The cause of the accident is under investigation.