A man and a woman were forced to jump from a second floor window.
Firefighters went door to door to rescue several other people from their apartments inside the New Horizons Housing building at 48th and Trinity Place.
The Red Cross says 28 people were displaced by the fire, while the Red Paw organization says it's taking care of at least 12 pets, mostly cats.
Two women are in the hospital.
Firefighters have not determined the cause yet.
Investigators say the blaze may have been intentionally set.