A wildfire fanned by unprecedented December Santa Ana winds was running unchecked across the North County Thursday, chewing through neighborhoods and prompting thousands to flee as the flames spread dangerously fast toward the more populated coast.

By 8 p.m., the Lilac fire had grown to 4,100 acres and had zero containment, adding to the conflagration of wildfires wreaking havoc across Southern California this week.

And as of midnight, county officials confirmed that the county had called more than 100,000 phone numbers to issue evacuation orders or warnings through AlertSanDiego, a regional notification system.

At least three civilians trying to evacuate were injured in the blaze, which roared through Bonsall — a rural community of horses, livestock and agricultural lands — and into Oceanside. A fourth civilian suffered smoke inhalation. Gov. Jerry Brown declared a state of emergency in the county.

“We are in no way near the end of this,” warned Ron Lane, the county's deputy chief administrative officer who oversees public safety.

Large swaths of Bonsall and Oceanside were evacuated, and authorities warned residents to be on high alert overnight.

“Its incumbent on all the people in this area to stay alert, stay informed and, if you feel it's important, self-evacuate and get out of the way of this fast-moving fire,” said Sheriff Bill Gore. “...Don’t necessarily wait for that deputy to knock on your door. There aren’t that many of us out there.”

As of about 12:30 a.m. Friday, some 578 people had checked into evacuations centers, a county spokeswoman said.

Evacuation centers in Carlsbad and Oceanside had reached capacity late Thursday, and evacuees were being directed to go to the overnight Red Cross shelter in Escondido at East Valley Community Center, 2245 East Valley Parkway.

At about 2 a.m., officials announced they had opened up a pet-friendly shelter at Palomar College, at 1140 W. Mission Road in San Marcos.

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Authorities confirmed 20 structures have been destroyed and 12 damaged, but witness accounts and news footage made it clear the count was much higher.

As night fell, a shopping center was being consumed by the blaze.

At the Rancho Monserate Country Club, a swath of upscale mobile homes bordering a golf course had already been reduced to ash and twisted metal.

Flames roared through horse barns at the San Luis Rey Downs Training Center. Trainers tried to corral the horses but in the end simply let the panicked animals free — at the risk of being trampled themselves. At least 25 horses reportedly died at the training center in Bonsall, where nearly 500 horses are stabled, officials said.

Streets were choked with good Samaritans hauling horse trailers, offering their services to help comrades evacuate their animals.

Horses were being accepted at the Del Mar Fairgrounds, which had taken in about 500 animals by shortly after midnight.

The Lilac Fire started Thursday off south Interstate 15 in the Bonsal area quickly burned more than 2500 acres, destroying 45 structures and threatening 1000 others, fire officials said. (John R. McCutchen, Howard Lipin, K.C. Alfred, Charlie Neuman, Hayne Palmour IV, Gina Ferazzi, Robert Gauthier, Eduardo Contreras, Alejandro Tamayo, Paul Sisson) (John R. McCutchen, Howard Lipin, K.C. Alfred, Charlie Neuman, Hayne Palmour IV, Gina Ferazzi, Robert Gauthier, Eduardo Contreras, Alejandro Tamayo, Paul Sisson)

Some residents decided to stay behind to do what they could. Susie and Michael Lynn stood on the dirt road leading to their home, putting out small spot fires with garden hoses.

The couple were working at the horse training center when they saw a huge cloud of smoke billowing near their neighborhood.

“We saw it getting the better of the firemen and it was heading our way,” said Susie Lynn.

Many roads were closed, including portions of state Route 76 and Old Highway 395.

Eleven school districts will be closed Friday: Bonsall Unified School District, Fallbrook Union Elementary School District, Fallbrook Union High School District, Julian Union Elementary School District, Julian Union High School District, Mountain Empire Unified School District, Oceanside Unified School District, San Marcos Unified School District, Spencer Valley School District, Vista Unified School District and Warner Unified School District as well as Guajome Park Academy, a charter school.

Cal State San Marcos will also be closed, as well as several Palomar College satellite campuses.

The fire was being fed by 35 mph-plus winds, although that’s not nearly as fierce as the strongest gusts in the county Thursday, recorded at 88 mph at Sill Hill near Descanso. The Santa Anas come on the heels of a record-hot summer and are paired with humidity in the single digits.

“These are conditions we haven’t seen in many, many years,” Cal Fire Capt. Kendall Bortisser said.

The conditions were expected to improve overnight, giving firefighters hope they could get ahead of the blaze’s run toward the coast, but onshore winds were anticipated Friday, complicating the situation.

The fire was reported about 11:30 a.m. off Interstate 15 south of state Route 76. The blaze, a couple acres by the time fire crews arrived, quickly grew to 75 acres, then 500.

At least 700 firefighters from agencies across the county were called to duty, as well as two San Diego Fire-Rescue Department helicopters granted permission to fly at night. Tankers and helicopters, including those owned by the military and San Diego Gas and Electric, pitched in with water and retardant drops earlier in the day and were expected to resume at daybreak.

Besides the civilian injuries, one firefighter suffered smoke inhalation. Another who dislocated his shoulder popped it back in and resumed work, authorities said.

Nearly 20,000 SDG&E customers were without power by Thursday afternoon, most affected by the utility’s decision to kill power in backcountry areas experiencing the worst winds. The power in some areas could remain out for the next few days, as the dry, windy conditions have prompted the National Weather Service to extend its red-flag warning through Sunday.

“We have a long road ahead of us,” Cal Fire Battalion Chief Nick Schuler said Thursday night.

The blaze overwhelmed 911 dispatchers, and authorities urged residents to call the county’s 211 line for information on the fire. But the 211 line had its own issues, as several callers reported they could not get through.