LYNN – A stubborn fire consumed a Norton Street home early Tuesday afternoon, sending residents in the congested neighborhood scurrying for safety and raising questions about its origin.More than an hour after the first fire engines arrived, flames still licked the eaves and showed bright orange through the disintegrating exterior walls of the house at 9-11 Norton St.Most of the firefighting was done from an aerial platform since the roof threatened to collapse. Firefighters with hose lines were unable to battle the blaze until the upper levels of the structure toppled.Arson investigators were on the scene, waiting for the initial overhaul to be completed before entering the building to look for signs of foul play or evidence of how the fire started.Fire Lt. David Legere, head of the city’s arson squad, said the fire may have begun on the first floor where occupants reported a smoke detector sounding.”We have a pretty good idea of where it started,” Legere said. “But we won’t know (a cause) for sure until we go back tomorrow.”According to Legere, eight residents on the second floor heard the alarm and made it out of the house by walking through the smoke to the front door.Although fire officials believe everyone in the home got out unharmed, a secondary search was being readied as the flames died down. Children who live at the address were at school when the fire broke out, Legere said.At least one firefighter reportedly was taken to the hospital for a hip injury.The three-story structure was aluminum sided, which contained the heat of the fire.The state’s Fire Marshall’s Office will return to the house today to investigate in an attempt to determine the official cause of the fire.- Item staff reporter Dan O’Brien contributed to this report.