Fire officials say a deadly blaze that claimed the lives of three Durham Region teenagers was not suspicious in nature, but it is still unclear whether the smoke detectors in the building where they died were working.
The fire broke out in the early hours of Sunday morning in a home in Whitby, Ont., that was divided into several rental units.
Someone inside the home called 911 at about 12:25 a.m. ET. While firefighters made it to the burning building quickly, three people inside could not be saved.
Whitby fire Chief Michael Gerrard said firefighters faced challenges in reaching the victims, who were on the upper floor of the building.
"It was extremely difficult for the crews to get upstairs because they had to go through fire, which was at the front of the building, for them to get to the second storey, and then get to the back where the victims were found," Gerrard told CBC News.
While the names of the deceased have not been officially released, CBC News has learned that two young women were visiting a male friend who lived in the upper floor of the home.
One of the young women was a student at Henry Street High School. The male who died in the fire was working towards his high-school diploma at Anderson Collegiate. Grief counsellors have been brought to both schools to help students cope.
Post-mortem examinations of all three victims were expected to take place on Monday.
A day after the fire, crews were seen boarding up the windows and putting a tarp over the roof of the burned-out building.
The blaze remains under the investigation by the Office of the Fire Marshal. Investigators will return to the scene on Tuesday, as they try to determine what caused the fire and why the victims did not make it out alive.