Police now say all of the occupants of a home destroyed by fire have been accounted for.
Crews were called to the 100 block of Windermere Road S.W. shortly after 1:30 p.m. MT. There was smoke coming from the basement but the heat from the fire was so intense firefighters were unable to enter the home.
Three people were reported to be inside at the time. One was initially missing but was found by police.
Investigators are in the process of interviewing the occupants and the arson unit is also investigating.
Intense heat caused a flashover, which occurs when temperatures get so high that materials ignite with explosive force.
Thermal imaging cameras showed the temperatures in the home to be about 870 C.
Crews had to be rotated several times because of frigid temperatures and some firefighters fell on the ice while attacking the blaze, though no injuries were reported.
Firefighters will remain on scene throughout the night.