The Fresno Fire Department says the fire started in a patio and extended into two of the six apartments. A total of four units were damaged. Crews were able to quickly knock down the flames before they spread into the other units.
One resident was treated at the scene, and a second was taken to a local hospital, according to the fire department.
Between six and 10 people have been displaced. The Red Cross was called in to help them.
Investigators say the cause of the fire is potentially suspicious.