The fire at 1831 Balboa St. near 19th Avenue was reported at about 4:40 a.m., Smith said. The three-story house shares a wall with a neighboring, two-story residential building, Smith said.
The fire started in between the two homes, engulfed the house at 1831 Balboa St. and quickly spread next door, Smith said.
Smith said 67 firefighters responded to the fire and controlled it around 5:05 a.m.
No residents were injured, but five were displaced, according to Smith. American Red Cross was on the scene to assist, Smith said.
One firefighter was injured when a piece of debris fell on his head. He was transported to a nearby hospital as a precaution, Smith said.