Intense heat and smoke drove back neighbours who tried to rescue Colin Coombs from the blaze in a downstairs room at a terraced house in Kensington, Liverpool.
Firefighters forced their way into the room and carried out Colin, but they were too late to save his life.
His 21-year-old mother, Samantha, who was unable to reach her son but raised the alarm, was being comforted by social workers at Alder Hey Children's Hospital.
Detectives, forensic experts and a fire investigation team were examining the house in an attempt to establish the cause of the blaze. 'It is being treated as suspicious because of the ferocity of the fire in such a short space of time,' a spokesman said.