At least eight persons have been killed and over 50 injured in a fire that broke out at a two-storey building in Portugal, the media reported.The fire broke out on Saturday night in a building in Vila Nova da Rainha, 250 km from Lisbon, after a heating-boiler exploded, Xinhua news agency reported.The National Civil Protection Authority sent 148 firefighters and 67 vehicles to the scene and the blaze was contained within an hour.Some of the injured, suffering from serious burns, were taken to hospitals by rescue helicopters.