At least 13 people were killed and six injured when fire broke out on Saturday night during a birthday party at a bar in French city of Rouen, Interior Minister Bernard Cazeneuve said.More than 50 firefighters were called to douse the flames at the Cuba Libre bar. Reports suggest candles on a cake may have started the fire, BBC reported.An inquiry was under way to determine the exact cause of the fire. Terrorism has been ruled out.The persons were believed to be killed by a poisonous gas emitted by a material in the ceiling which caught fire.Prime Minister Manuel Valls said: "Deep sadness with regard to the tragedy which mowed down 13 young lives. Compassion and support for the afflicted families."