The second victim of the fire died in hospital, Ontario Provincial Police said in a statement on Monday.
Kawartha Lakes OPP said in a media release Monday afternoon that a staff member at the youth facility has died of injuries sustained in the fire.
Police were called to a disturbance at the facility, located at 725 Quaker Rd., at about 3:30 p.m. OPP say the structure was on fire and fire and ambulance crews were then called to the scene. One person from the facility was pronounced dead on Friday. Two other people were taken to hospital with injuries.
A youth was charged on Saturday with second-degree murder, and now faces another second-degree murder charge, as well as arson causing bodily harm.
OPP are not releasing any information about the victims.