A Calgary woman in her 40s has died after being found unconscious at the scene of a fire in the northwest.

Fire crews were called to a duplex in the 4300 block of Bowness Road around 11 p.m. Thursday night.

The Calgary Fire Department says firefighters noticed thick black smoke coming from one side and when they entered the unit, they found the woman in the basement.

The arson unit is now investigating.

An autopsy will take place later today.