A mid-afternoon fire Friday at 214 Olive Street in Paso Robles destroyed unit A of a duplex in Paso Robles.
The cause of the fire was under investigation, said Paso Robles Fire Department Battalion Chief Kevin Taylor.
No one was home at the time of the fire, which spread to dry grass outside the home, where firefighters extinguished flames with a garden hose.
Firefighters from Cal Fire, Templeton and Atascadero responded to the blaze.
It took firefighters about one hour to knock down the fire, which at times sent flames cresting above the rooftop of the residence.
Firefighters had to break windows and chainsaw a hole in the roof of the residence to release heat and smoke from inside.
Neighbors in a nearby unit evacuated their pets.
It was unclear how much damage was done to the structure and its contents, Taylor said.