The "Camp Fire" - as named by local officials - is expected to grow because of high winds and current dry conditions in the area.
Butte County supervisor Doug Teeter said authorities used a bulldozer to push abandoned cars out the way to reach Feather River Hospital and evacuate patients as flames engulfed its old wing and the roof of the emergency department.
Neighbourhoods, schools and hospitals have been evacuated while some residents in the town of Paradise were trapped by the flames, officials say.
"We're trying to get as many people out as quickly as possible and save as many lives as we can", he said.
Plumes of smoke loom in the sky several miles away, seen behind a home in Thousand Oaks, Calif., as a wind-driven wildfire known as the Hill fire threatens the area late Thursday afternoon, November 4, 2018. By Thursday afternoon, the fire was growing at the rate of about one football field every three seconds, assisted by dry conditions and wind gusts of up to 65 miles per hour.
The Camp Fire rages through Paradise, Calif., on Thursday, Nov. 8, 2018. God help us!' Bernacett said before breaking down crying.
Fossil Sport Smartwatch now available with Snapdragon Wear 3100 processor
It's November, and new Wear OS-compatible smartwatches keep dribbling out as we approach the holidays. Fossil's own sub-brands are even guilty of this.
Shari Bernacett said her husband tried to get people to leave the Paradise mobile home park they manage.
A fast-moving wildfire roared through a Northern California town on Thursday, with reports of fatalities as it burned hundreds of homes and sent tens of thousands of people fleeing 50-foot-high (15.25-metres-high) flames, authorities and a Reuters witness said. The whole hill's on fire.
Cal Fire tweeted that the fire was "very dangerous" and urged people to follow evacuation orders.
At least one nursing home and hospital were evacuated and several homes were on fire, according to the Sacramento Bee, and the region is covered with thick, dark smoke.
A Red Flag Warning is in place through Friday morning in the Butte County area, and winds are expected to gust at speeds as high as 40 miles per hour overnight, according to the National Weathers Service.
"It's very chaotic. It's a very bad fire", Officer Ryan Lambert of the California Highway Patrol said of the evacuation.