Fire officials said crews responded to the two-alarm house fire around 12:30 a.m. in Pittsburg, about 40 miles east of San Francisco.
Firefighters put out the blaze within 30 minutes, but they couldn't save the three victims, who were apparently trying to escape the flames, authorities told the Contra Costa Times.
Their identities have not been released, but neighbors said they are believed to be sisters in their 60s and 70s.
One woman was found in a back bedroom, and the two others were in the kitchen. Firefighters carried them out and tried unsuccessfully to revive them, said Fire Marshal Lewis Broschard of the Contra Costa County Fire Protection District.
Crews found three smoke detectors inside the single-story house, but none of them had batteries, Broschard said. Uninstalled detectors were found in the laundry room.
"That's the sad part here. Had the smoke alarms had batteries, the women would have had some warning," Broschard told the San Francisco Chronicle. "But unfortunately by the time they knew there was a fire, it was too late. The fire had a head start."
Fire officials are investigating the cause of the blaze, which is believed to have started in the front room.
Mary Lou Oliver's neighboring home sustained some exterior damage from the blaze, but she said she feels fortunate that neighbors pounded on her door to wake her up.
"Someone knocked on my door and said, 'Your house is on fire!' " Oliver told the Chronicle. "I grabbed my purse and my Chihuahua and got out ... It's so tragic the women next door couldn't have been notified sooner."