A man's body was found at the scene on the 5800 block of Bowcroft Street.
Firefighters arrived at the two-story four-plex just before noon Sunday.
The fire was put out in about 15 minutes. Arson investigators were called after a man's body was found in a downstairs unit.
Firefighters said the home had a smoke alarm, which was functioning at the time of the fire.
They also said there were no bars on the windows, security doors or obvious non-fire factors to stop the man from getting out.