The Yukon's Fire Marshal says the deaths of the five people in a home in Porter Creek were accidental and caused by an ice blockage in the top two feet of the chimney.

Valerie and Bradley Rusk, their two children, Gabriel, 13, and Rebekah, 11, and family friend Donald McNamee were found dead in their rented house on Jan. 29.

The Fire Marshal's office (FMO) has been investigating ever since, and has now submitted its investigation report to the Yukon coroner's office and the RCMP.

The report concludes that the ice blockage contributed a build-up of noxious gases, including carbon monoxide in the Centennial Street house.

The report, a summary of which was released Friday, also determined that the inner lining of the brick chimney had deteriorated and debris was found at the lowest point in the chimney.

This brick and mortar debris obstructed and slowed the flow of flue gases from the furnace to the exterior of the house.

"Low temperature flue gases coming from the high-efficiency burner in the boiler combined with the extremely cold temperatures at the time contributed to the build-up of ice. The combined factors were determined to be the cause of this tragic incident,” the report concludes.

Last week, the territory's coroner confirmed three of the five people in the house had extremely high levels of carboxy hemoglobin in their systems.

Carboxy hemoglobin is a mix of carbon monoxide and hemoglobin in the blood stream. High levels prevent oxygen from being carried through the body.

Anything exceeding 40 per cent is considered severe poisoning, while anything around 60 per cent is likely to be fatal.

Valerie Rusk had levels in the 80s. Her children's levels were in the 90s.

Results for the other two people have not been released by the Vancouver lab yet.

When fire officials entered the home, carbon monoxide levels were 10 times what would set off a standard alarm.

Officials are advising homeowners and renters to check their homes for hazards and install carbon monoxide and smoke detectors.

"The FMO recommends that residents, whether homeowners or renters, please check for icing on your chimney, especially during cold snaps, and ensure you have properly installed carbon monoxide and smoke detectors,” said Fire Marshal Dennis Berry said.

"We also recommend that people ensure their heating system is property serviced and maintained on a regular basis.”