The woman was identified as Erica Vencill and her daughter was identified as Rachel Vencill. The two are expected to recover, but they remain hospitalized. Three children and two adults were also treated a local hospital, but they were treated and released.
Fire officials said the fire happened when a woman lit a cigarette in a unit where natural gas was leaking. However, the state fire marshal's office said Wednesday that it was not ready to confirm a cause.
Jamie Cairy, who lives nearby, recorded the explosion on home video camera.
Ten units in a two-story building were either destroyed or heavily damaged. The American Red Cross is helping with shelter for displaced residents.
Fire officials said smoke alarms were present in the complex and were sounding were firefighters arrived at the scene.