The fire started around 7:30 pm at the Los Flores Apartment near First Street and Shields Avenue.
When the first firefighters arrived, they burst into an apartment to rescue a 5-year-old girl.
The Fresno Fire Department originally described the girl as a toddler, but has since clarified her age.
"Anytime there's reports somebody's trapped inside a structure fire the number one priority is life safety," said Josh Sellers with the Fresno Fire Department.
"So, we're going to try to aggressively get inside and get that person or people out."
The girl, her mother, and a 7-year-old were all taken to the hospital, where the 5-year-old remains in critical condition.
The firefighter believed to have saved the girl was also treated and released from the hospital for burns.
Firefighters say the fire started on the second story, displacing 10 people and killing two dogs.
The Red Cross is searching for temporary homes those who were displaced.
Investigators are still working to figure out what caused the fire.
Stay with Action News for the latest updates on this developing story.
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