A gas cylinder exploded in southern Pakistan on Tuesday, killing four people and injuring seven, AP quoted police as saying. It was not immediately clear what caused the blast near a shop in the commercial area of Shirin Jinnah Colony in Karachi, the capital of southern Sindh province, and an area police chief Arif Razzaq said officers were still investigating. The dead and injured have been rushed to a hospital, he said, without giving any further details.