Crews were summoned to a townhouse in an apartment complex at 1732 Mission Blvd. on reports of a fire around 10:30 p.m., according to the Santa Rosa Fire Department.
Firefighters arrived on the scene to find heavy fire on the second floor of the townhouse, and were able to get the blaze under control in about 20 minutes, fire officials said.
As crews battled the fire, a skirmish broke out between two men living in the townhouse. Firefighters and police at the scene broke up the fight, officials said.
No injuries were suffered in the fight, but one of the home's three residents was treated at the scene for minor smoke inhalation.
All three were displaced, and the Red Cross was called to assist the residents with temporary housing.
Fire personnel said an initial investigation revealed that unattended burning candles may have caused the blaze, but the official cause has not been determined.
The fire caused roughly $40,000 in damage to the building and its contents, according to the fire department.