Police say an autopsy will be necessary to confirm if the bodies are those of the two missing children, aged 3 and 4.
The large and stubborn fire began at about 3:30 p.m. and firefighters from several communities continued to battle the flames late into the night.
Quebec provincial police said two adults and one child managed to escape the blaze and were taken to hospital for shock and smoke intoxication.
A spokesman said Friday the exact cause of the blaze remains unknown, but it does not appear to be a criminal act.
The fire, about 90 kilometres north of Ottawa, comes less than a week after another house fire in Gatineau, Que., claimed the lives of 12-year-old twins.
On Wednesday, four boys aged 9, 11, 12 and 15 died when their home in southern Manitoba burned to the ground.
And, a house fire earlier this month on a reserve in northern Saskatchewan claimed the lives of a two-year-old boy and his 18-month-old sister.