Vitor Vitinha said his cousin Bruno lost two children as Trévoux mourns after an explosion investigators say was caused by a woman releasing gas in her apartment.Two young brothers, aged three and five, died and about a dozen people were injured when the blast destroyed part of a four-story building, leaving 22 apartments and seven houses uninhabitable and blowing out windows at nearby schools.Authorities have opened an inquiry in Bourg-en-Bresse, deployed about 50 firefighters, 36 vehicles and 45 gendarmes, arranged shelter and psychological support for displaced residents, and warned casualty figures remain provisional.