Two people were killed and another two injured in a shipyard explosion in Shanghai on Monday, local work safety authorities said. The explosion occurred at about 7:40 a.m. at the Huarun Dadong Dockyard Co., Ltd. in Chongming county, Xinhua quoted the Shanghai Administration of Work Safety as saying in a statement. The explosion was triggered by natural gas leak during cutting operations of the shipbuilding process, it said. A further investigation into the cause of the accident is under way.