A quick-moving wildfire is churning through the foothills of Southern California, forcing local authorities to issue mandatory evacuations for some 100,000 people in the San Fernando Valley north of Los Angeles.

The blaze, which officials have named the Saddleridge Fire, ignited late Thursday in the city of Sylmar. By Friday morning, it had torched roughly 4,700 acres, according to the latest alert by the Los Angeles Fire Department.

"This is a very dynamic fire," Los Angeles Fire Chief Ralph Terrazas said at a Friday morning press conference.

At least 25 structures have been destroyed and more property assessments are planned throughout the day.

Emergency officials say one civilian went into cardiac arrest and died at the hospital, and one firefighter sustained a minor injury to his eye. The officials did not provide details about those cases.

No cause for the fire has been determined. Terrazas said emergency officials received the first reports of the fire around 9 p.m. Thursday and that it was located near the 210 freeway at the Yarnell Street exit.

"Our first arriving companies reported significant fire with multiple homes threatened," Terrazas said. "We went into an aggressive offensive attack while simultaneously setting up our structure protection."

LAFD reports the fire is at 0% containment, with more than 1,000 firefighters assigned to combat it. Personnel from the Los Angeles Police Department, Los Angeles County Fire Department and U.S. Forest Service are on the scene, helping with the effort.

"Super scoopers and the Sky Crane are in operation this morning," LAFD said.

Strong Santa Ana winds, coupled with the area's dry chaparral landscape, have helped fuel the fire. The flames have forced the closure of several miles of the 118 and 210 freeways. Evacuation orders affect communities on both sides of Interstate 5 in the northernmost city in Los Angeles County.

The National Weather Service said a wind advisory and a red flag warning are in effect.

"A moderate to strong Santa Ana wind event will continue to bring dangerous fire weather conditions to most of Los Angeles and Ventura Counties through late Friday afternoon," NWS said in its latest alert.

The agency adds, "Wind gusts between 45 and 55 mph are expected across coastal and valley areas, with gusts between 55 and 75 mph in the foothills and mountains."

NWS warns that windy, dry conditions will bring the "potential for very rapid fire spread, long range spotting, and extreme fire behavior."

Earlier Friday, LAFD tweeted that some evacuation centers like one at Granada Hills Recreation Center were full, but it added that others were opening up.

For days, California utility companies have been preemptively cutting off power out of fear that high wind gusts could blow power lines into trees, sparking dangerous fires.

Southern California Edison cut off power to more than 21,000 customers under its Public Safety Power Shutdown in Kern, Los Angeles, Riverside, San Bernardino and Ventura Counties.

The utility also said it is considering shutting off another 223,000 customers power.

Gas utilities are also taking action. As the LAist news site reports:

"SoCalGas officials said personnel at their gas storage facility at Aliso Canyon had been evacuated by fire authorities. In an email responding to questions, they said multiple fire engines and firefighters from the city and county were fighting the fire "in and around the Aliso Canyon facility."

Earlier in the week PG&E, the state's largest utility began proactively shutting off power to roughly 800,000 customers in Northern and Central California, impacting nearly 2.5 million people, according to one estimate.

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