LEWISTON – A 5-year-old boy killed in an apartment house fire started the blaze by playing with matches, investigators said Tuesday.

Anthony Lilly safely exited the apartment with his parents, but he ran back inside and was later found by firefighters on the living room floor Monday morning, said Stephen McCausland, spokesman for the Maine Department of Public Safety.

The boy, who was unconscious when he was found, died later at the Central Maine Medical Center. His father, who returned to the burning apartment to try to rescue the boy, remained hospitalized Tuesday with second- and third-degree burns.

The boy’s parents did not realize that their son had run back into the apartment house until it was too late, said Anthony’s uncle, Harold Lilly. “When they opened the door, they were blasted with smoke,” Harold Lilly told WMTW-TV.

The source of the fire was a mattress that caught fire as Anthony Lilly played with matches, fire marshal investigators said.

His death was the 14th related to a fire started by a child playing with matches or lighters since 1990, said Maine Fire Marshal John Dean.

Like many children, Anthony Lilly had shown an interest in fire, Dean said. Children are often fascinated by fire, and parents must be constantly aware of the potential for children playing with matches or cigarette lighters, he said.