Flames and smoke killed Homewood firefighter Brian Carey and an elderly man who lived the home.
ABC 7 News has learned a report from the federal Bureau of Alcohol Tobacco and Firearms says there was so much damage in the home -- and so little left of what was inside -- investigators can't determine the origin of the fire.
However, they were able to determine the fire was not caused by a short in an electrical lift chair or made worse by an explosion of oxygen tanks kept inside the home.
Another federal agency is reviewing how firefighters battled the blaze. That report is expected to be released in the next month.