Wildfire tears through San Diego County

A structure burns at the so-called Lilac Fire in the early morning hours of Dec. 8, 2017 near Bonsall, California.

Authorities issued mandatory evacuation orders for nearly 20,000 county residents as wildfire chewed up more than 4,000 acres on its way west toward Camp Pendleton and the city of Oceanside. At least 1,000 homes and other structures were in imminent danger, the California Department of Forestry and Fire Protection said.

Trees glow in the wind after being burned by the wildfire on Dec. 7.

Firefighters walk to the fire line on Dec. 7.

A helicopter flies over the wildfire on Dec. 7.

The wind-swept blazes have forced tens of thousands of evacuations and destroyed dozens of homes in Southern California.

A firefighter works on extinguishing part of the wildfire on Dec. 7.

Firefighters work to save a home from an encroaching fire on Dec. 7.

A firefighter watches the fire line on Dec. 7.

Fire personnel drive along West Lilac Road in the midst of the wildfire on Dec. 7.

Firefighters prepare to battle the wildfire that quickly spread through the area on Dec. 7.

A firefighter sprays water on a burning structure on Dec. 7.

A water bomber drops fire retardant over the wildfire on Dec. 7.

Cars and a residence burn as a result of the fast moving wildfire on Dec. 7.

Firefighters jump a fence to try and save a burning home on Dec. 7.

Terrified horses gallop from San Luis Rey Downs as the wildfire sweeps through the horse-training facility on Dec. 7.

Trainers at the racehorse training center said at least a dozen thoroughbreds died when hundreds of horses sprinted from the flames, The San Diego Union-Tribune reported.

Spectators watch from Old Highway 395 as smoke rises from the wildfire on Dec. 7.

Photos: Wildfire devours homes in Southern California