Methane leaking from sewage pipes killed two workers and injured four others Sunday at a subway construction site in southern Chinese city of Shenzhen. Four injured were hospitalized and they no longer face life-threatening danger, Xinhua quoted sources of the construction company Shenzhen Water Project Engineering Co. Ltd. as saying. The accident occurred Sunday morning at Daxin station on the subway's extension line under construction. Authorities are still probing the case.