LOS ANGELES — Firefighters battled to hold back flames that on Thursday threatened tens of thousands of homes in Southern California and forced new evacuations, as officials implored residents to remain vigilant in the face of a rash of wildfires across greater Los Angeles that will quite likely not abate for days.
More than 200,000 people in Los Angeles and Ventura Counties have been told to leave their homes. The city of Ojai, nearly surrounded by fires, was evacuated on Thursday, as were parts of the coastal city of Carpinteria. And hundreds of schools were closed and roads were blocked. With well over 100,000 acres scorched, residents were on edge, watching the news footage of hills and canyons going up in smoke.
Across seven counties, millions of cellphones shook and squawked with a warning of “extreme fire danger,” in California’s largest-ever use of a disaster alert system. Other automated alerts warned people to pack up food, water and essential documents, and to be ready to flee on a few minutes’ notice.
The bone-dry Santa Ana winds blowing from the northeast picked up speed, gusting to 60 miles per hour in places, adding to firefighters’ struggles with thick brush and rugged terrain, though it did not reach the extreme speeds forecasters had feared. Officials warned that with several large fires that were still burning (and no more than 15 percent contained), as well as winds that, though easing a bit, were expected to remain high on Friday, dangerous surprises could still be in store.
As if to illustrate the danger, several new fires cropped up across Southern California. A fire near Bonsall in San Diego County ignited and within hours spread to more than 4,000 acres with zero containment. It injured at least three people as hundreds of residents were forced to evacuate and at least 20 structures were destroyed.
Gov. Jerry Brown declared an emergency in San Diego County on Thursday evening as local officials there widened the evacuation zone and warned that conditions were expected to worsen.
It wasn’t all bad news, though. By Thursday night, several top local and state officials said they were encouraged by improving conditions in the city and county of Los Angeles. And as a result, officials announced that some Angelenos would be allowed to return home starting Thursday evening.
• Officially, the fires have destroyed more than 400 homes, businesses and other buildings, and damaged others. Emergency workers say that number could rise as they re-enter the charred areas.
• The threat was so severe that for the first time, state officials used the highest category in their color-coded fire hazard warning system. They painted much of Southern California purple on Thursday, for extreme danger, and many people received warnings to be ready to flee. Here’s what to do when you’re preparing to evacuate.
• Late Thursday, with the fire that began in Ventura threatening scores of homes, Mr. Brown extended a state of emergency declaration to Santa Barbara County. He also requested an emergency declaration from the president that would make it easier for federal aid to reach Southern California.
• Hundreds of schools were ordered closed for the rest of the week because of the thick blanket of smoke filling the skies. The Los Angeles Unified School District said at least 322 schools canceled classes on Thursday and Friday.
• Some residents who were forced to evacuate their homes because of the fires in the San Fernando Valley and in Bel-Air were told they could return on Thursday night. Charlie Beck, the chief of the Los Angeles Police Department, said an “inordinate amount” of police officers would be present as the repopulation took place.
• Eric Garcetti, the mayor of Los Angeles, said late Thursday that he was not aware of any human deaths connected to the Los Angeles fires. But Daryl L. Osby, the chief of the Los Angeles County Fire Department, confirmed reports that horses had perished.