The two-alarm fire was reported at 1:41 a.m. at a home in the 2500 block of Etna Street, Assistant Fire Chief Sabina Imrie said.
The elderly couple living in the home were alerted to the blaze by smoke detectors. They escaped uninjured, Imrie said.
Investigators believe a cigarette that was not fully extinguished sparked a fire on the second story of the home, according to Imrie.
Firefighters responded within minutes and controlled the blaze.
The fire caused an estimated $500,000 in damage to the structure and $200,000 to the home's contents, Imrie said.
The elderly couple have been displaced and are staying with neighbors, she said.
Firefighters were able to save an adjacent home that was initially also in danger of catching fire.
The neighboring home sustained "very little scorching," but three windows were cracked due to the heat from the blaze, according to Imrie.