Firefighters say the victim is a 60-year-old woman. Crews located the woman inside the home, who they say wasn't breathing. They initiated CPR but she was pronounced dead at the scene.
Officials searched for the other occupant of the home.
The fire was contained in 45 minutes and crews spent several hours putting out hot spots throughout the building.
Investigators are working to determine what started the fire. No cause has been confirmed.
1 person killed in 3 alarm fire on Oak Street in San Mateo. pic.twitter.com/C9AAm9f3oB— Matt Keller (@MattKellerABC7) November 25, 2016