Trapped upstairs as flames shot through their side of a two-family house in South Plainfield, N.J., five people — a 62-year-old woman and four of her grandchildren — died early Thursday, the authorities said. “The house is gutted,” the borough administrator, Glenn Cullen, said. The five victims — a 12-year-old girl; three boys, ages 4, 5 and 7; and their grandmother, whom the authorities identified as Ann Jefferson — apparently faced an inferno made hotter by bricks between the walls that provided structural support to what looked like a clapboard house. Captain Joseph Abbruzzese, of the South Plainfield Fire Department, will bring 50 Hugs teddy bears to the family, friends and appropriate schools for counselors to use as local children begin the process of grieving for their lost classmates.