Two young boys killed in a devastating Oshawa, Ont. house fire that resulted in the deaths of four people have been identified by friends and family.

The fire broke out in a stretch of row homes on Olive Avenue, in the area of Simcoe and Ritson roads, on Monday at 1 a.m.

Five people were rescued from the home and taken to hospital. But in those initial hours, four others were unaccounted for.

By Monday night, the bodies of the two men were found and roughly 24 hours later the bodies of the two children were found.

Friends and family told CTV News Toronto on Wednesday that the two children found dead were brothers, and identified them as Christian Sterling and Lucas Sterling.

Lucas Sterling, left, and Christian Sterling, right are seen in this undated photo. (Supplied)

The boy’s ages are not known at this time.

Police said the two other bodies were adult males unrelated to the family. Those men have not been publicly identified.

Several family members told CTV News Toronto that three young boys – including Christian and Lucas – lived at the home with their parents, grandfather and at least two boarders.

Police investigating if fire was arson

The major crime unit has launched a formal probe into the fire after police received information at the scene that the incident could be an arson.

“There was information that the officers received at the time when we were doing, in the initial recovery stage, that it could have a potential to be an arson and then at that point our investigators then prompted an investigation to be commenced,” Durham Regional Police Acting Sgt. George Tudos said Wednesday.

oshawa fire

Tudos said police would continue their investigation on Wednesday and gather evidence at the scene.

“Now we will be looking for judicial authorization to enter that residence to collect more evidence to support our police investigation, but right now it's still early in the investigation, and our investigators will have to determine, based on any other evidence that we find now, whether it falls in the category of being criminal or not criminal,” he said.

-With files from CTV News Toronto's Katherine DeClerq and Miriam Katawazi.