Investigative authorities on Tuesday launched a compulsory investigation into the death of a worker in a collapse accident at a subway construction site in Seoul two weeks ago. The prosecution, police and labor ministry said they jointly raided POSCO E&C, the general contractor for the Sinansan Line, and its subcontractors. The new railway is currently under construction to link Seoul's Yeouido and Siheung and Ansan, both south of the capital. The collapse accident occurred at the Sinansan Line construction site near Yeouido Station on Dec. 18. Seven workers were initially trapped and later rescued but one of them, a pump truck operator belonging to a subcontractor, died. The Seoul Southern District Prosecutors Office, the Seoul Metropolitan Police Agency and the Seoul Regional Employment and Labor Office held their first meeting on Dec. 22 to discuss the direction of the joint investigation, focusing on whether there were violations of the Serious Accidents Punishment Act and the Occupational Safety and Health Act. A prosecution official said the authorities will thoroughly investigate