The fire started 9:30 Wednesday night near Elizabeth and College in the Tower District.
42 firefighters responded to the two alarm blaze. When they arrived, flames could be seen shooting from both the bottom and top floors.
Three units were damaged by the fire, and three others by smoke and water.
Investigators say it started after a tenant left food on the stove.
Two people were taken to the hospital with burns and smoke inhalation.
The damage is estimated at $400 thousand.