Crews arrived at the duplex across the street from El Cajon Valley High School around 5:15 a.m. and were able to knock down the blaze in about 10 minutes.
One unit of the duplex was destroyed, but firefighters were able to keep the flames from spreading. Four people lost their home, including two children ages 10 and 13. Crews were unable to save the family dog during the rescue.
Most of East Madison Avenue was blocked off in the area as firefighters continued cleaning up.
The blaze caused an estimated $150,000 in damage to the apartment. The cause of the fire is under investigation.
The American Red Cross was called to help the homeless family.