Police were questioning four teenage boys, The Youngstown Vindicator reported.
The dead were identified as Carol Crawford, 46, her daughter Jennifer Crawford, 23, and Jennifer's four children, Raneija, 8, Jeannine, 5, Aleisha, 3, and Brandon, 2. Three people in the house, a man and two women, survived the blaze and were taken to St. Elizabeth's Health Center.
Police Sgt. Patrick Kelly said investigators have found signs an accelerant was poured on the front porch. The state fire marshal was to use a trained dog to search for accelerants.
The fire was reported at 5:30 a.m. and brought under control around 9 a.m.
Firefighters said that the victims were found on both floors of the two-story wood-frame building.