A three-alarm fire displaced a family of three Sunday afternoon after fire broke out in their two-story, single-family home in Acton, officials said. The Acton Fire Department responded to the blaze on Knowlton Drive around 2:44 p.m. after a neighbor called for help, according to a department statement. Heavy smoke and flames were coming from the back of the home when firefighters arrived. The fire was under control within an hour, officials said. No one was home when the fire started, and there were no injuries, the statement said. The American Red Cross assisted the family with housing needs Sunday. Employees from the Acton Department of Public Works used heavy machinery to tear down part of the back porch, securing the scene, officials said. Acton firefighters received help from nine nearby towns in fighting the fire, which remained under investigation Sunday.