Senior Fire Officer 1 Wilson Tana, arson investigator, identified the lone fatality as Argie Vidal.
He died of suffocation and sustained third degree burns.
Initial investigation showed that Vidal was with other children inside a two-story house at 1274 Wagas street in Tondo, when fire started at the second floor.
Based on the accounts of Warlito Artates, house owner and grandfather of Vidal, the victim was sleeping in one of the rooms.
He told investigators that the fire might have originated from the ceiling and may have been caused by faulty electrical wiring.
Fire Officer 1 Lords Hernandez, of the Manila City Fire Department (MCFD), said Vidal was sleeping at the upper floor and in the confusion, family members may have forgotten about him."
Hernandez said the blaze started at 1:25 p.m. and was immediately raised to the fourth alarm two minutes after receiving the distress call.
"We knew that the presence of more firemen was needed because it was a residential area and we had to prevent the fire from spreading to adjoining houses."
The fire was declared out at 1:47 p.m. Some 15 firetrucks and numerous volunteer fire brigades responded to the call.