PARADISE, Calif. — Fire conditions were moderate to extreme in Northern California late Saturday as the red flag warning went into effect at 10 p.m. Firefighters will continue to be affected by strong winds until the red flag warning ends Monday morning.

The amount of acreage burned increased to 109,000 acres overnight and is 25 percent contained. With 6,713 structures burned, 6,453 being homes and much of the town of Paradise, the Camp Fire supplanted the Tubbs Fire in Sonoma and Napa counties last year that burned 5,636 structures as the most destructive wildfire in state history.

Fire lines are being strategically placed ahead of the fire, Cal Fire officials said. With the northeast wind pushing smoke to the southwest, air operations will take advantage of the clearer air on the eastern side of the fire as long as weather and smoke conditions permit. Firefighters and other agencies are continuing to mitigate hazards in Paradise.

Air quality today is improved over yesterday, County officials said, but it is dependent on fire behavior and wind movement. Smoke may settle in the valley in the afternoon, evening and Monday.

The fire started Thursday at Camp Creek Road in the Feather River Canyon near Pulga. Investigators are looking at PG&E power lines as a possible cause of the fire. The blaze overran Concow, Paradise and Butte Creek Canyon in a matter of hours.

Fourteen fatalities were confirmed Saturday by Butte County Sheriff Kory Honea in the Saturday evening press conference. In addition to the nine dead confirmed Friday, the total of confirmed fatalities rose to 23.

Three firefighters have been injured, and 4,050 are fighting the blaze. In addition, there are 23 helicopters, 79 bulldozers and 512 engines assigned to the fire.