Investigators said the fire started outside Chelsea Park Apartments, 7351 S Catalpa Rd., shortly after midnight.
When firefighters arrived, they found an apartment on the second floor already engulfed in flames. Fire crews worked to rescue several people from the building before starting to fight the fire.
"We did have multiple rescues that took priority. We had two ladder rescues from adjacent apartments. We did also have two others who jumped prior to our arrival," said Battalion Chief Steve Prokopis, Unified Fire Authority.
The two people who jumped, along with someone who tried to catch them, suffered minor injuries. No one else was hurt, but firefighters said they had to evacuate everyone in the building, leaving about 100 people without a place to stay.
Utah Red Cross set up an evacuation center at the site. They are providing breakfast for the affected the residents and assessing their needs.
Crews hope some of those people will be allowed to return Wednesday morning.