A 17-year-old Michigan girl and her older brother were killed, and four others injured, when a bonfire lit to celebrate her high school graduation exploded. The brother had poured large amounts of gasoline on the two-story stack of wood, the Detroit News reported. Christopher Blewett, 27, was killed when his sister, Savannah Blewett, lit the end of a trail of gasoline that led through the grass to the wood pile, the St. Clair County Sheriff\'s Office said in a statement. The Saturday night blast in St. Clair Township blew out the windows at the back of their home, which was more than 100 feet from the bonfire, police said. Chunks of wood from the fire, built from pallets and construction material, were thrown more than 100 yards. The brother and sister were taken to a hospital, where they died. Three others were hospitalized with non-life threatening injuries. A fourth person was treated at the scene.