The fire at 2260 Wyandotte Street was reported around 5:18 p.m. Saturday, according to city spokesman Jaime Garrett.
Firefighters arriving on the scene found heavy flames coming from the building's second story, but were able to put the fire out just after 5:30 p.m.
Two residents were taken to a hospital with fire-related injuries and two firefighters suffered minor injuries in the blaze.
The residents of four units were displaced by the fire and are being assisted by the American Red Cross to find temporary housing.
