Firefighters responded to the fire in the 5700 block of Tucson Drive around 3:10 a.m., Capt. Rob Brown said.
Two of the four units in the apartment building were affected by the blaze, he said.
The fire started in a second floor unit and burned below to a first floor unit, Brown said.
There is minor to moderate damage to the two units that are considered uninhabitable, he said.
The fire was under control at about 3:45 a.m., Brown said.
A total of 15 people from all four units were displaced by the blaze because power and gas service had to be turned off, according to Brown.
Seven of the 15 people displaced are children, Brown said. The American Red Cross was called to assist them.
The cause of the fire is still under investigation and no injuries were reported.