LOS ANGELES — Around 50,000 people north of Los Angeles have been ordered to evacuate after a brush fire broke out Thursday afternoon, officials said.

The Tick Fire near Agua Dulce in northern Los Angeles County has destroyed several structures, the Los Angeles County Fire Department said. It had spread to nearly 4,000 acres and was zero percent contained Thursday evening.

It began at 1:42 p.m. near Tick Canyon Road in the Santa Clarita area, and numerous other fires have also broken out in the area, Los Angeles County Supervisor Kathryn Barger said,

While "numerous homes have been burned," Barger said, officials haven't yet been able to get an accurate damage assessment. "We know that at least six, but that number may rise," she said.

A man in the Santa Clarita area was stunned by the proximity of the flames on a ridge. "Woah, Lord. What are we going to do?" the man, who identified himself as James, told NBC Los Angeles as the sky filled with a smoky haze.

"This is the first time I’ve seen this going on. Oh my goodness," said the man, who has called the area home since 2006. "Wow. This is unbelievable. I’m about to leave — I can't stay."

More than 500 firefighters were working to combat the blaze Thursday as sustained winds of 20 mph and gusts of 40 mph were recorded, Los Angeles County Fire Chief Daryl Osby said. "We’re expecting stronger winds into tonight and into tomorrow morning," he said.

He urged people to stay aware even if they can’t see flames because there are plenty of hot spots.

"If you have not been evacuated, stay vigilant,” Osby said at a Thursday night news conference. "These things can occur quickly," he said.

That Tick Fire was one of several blazes in California fueled by high winds and low humidity, conditions that forecasters said were helping the fires grow. The National Weather Service said Santa Ana winds were gusting upwards of 45 to 55 mph across Los Angeles and Ventura counties.

In Northern California, around 2,000 people were ordered to evacuate in a rural part of northern Sonoma County after a fire broke out shortly before 9:30 p.m. Wednesday. It has grown to at least 16,000 acres, officials said.

Forty-nine homes or structures have been destroyed in the Kincade Fire, which broke out near the community of Geyserville, according to the California Department of Forestry and Fire Protection, also known as Cal Fire. The damage assessment is continuing.

The fire was 5 percent contained Thursday evening. Around 1,300 firefighters are on the line and that number is expected to increase Cal Fire Chief Mike Parkes said.

"Because of the terrain of the area, the crews had a difficult time getting around it early on, and the fire grew much more quickly in size," Parkes said.

No injuries have been reported in either fire.

The threat of wildfires prompted utility company Pacific Gas & Electric to pre-emptively shut off electricity to hundreds of thousands of people on Northern California on Wednesday to try and stop power lines from sparking blazes.

PG&E said in a regulatory filing with the state Public Utilities Commission on Thursday that it learned that a nearby transmission tower malfunctioned about seven minutes before the Kincade Fire erupted Wednesday night.

The utility said it learned from preliminary findings that a "transmission level outage" happened on a 230,000-volt line in the area at 9:20 p.m. Cal Fire says the Kincade Fire broke out at 9:27 p.m.

PG&E had shut off power to around 28,000 customers in Sonoma County, including in the Geyserville area where the fire began, but it did not de-energize transmission lines in the area.

"Those transmission lines were not de-energized because forecast weather conditions, particularly wind speeds, did not trigger the PSPS protocol,” PG&E said in a statement, referring to "public safety power shutoff," the term used for the planned blackouts.

"The wind speeds of concern for transmission lines are higher than those for distribution," the utility said in the statement.

The PG&E outages that began Wednesday were the second time in two weeks that the utility shut off power to large swaths of Northern California over fire risk.

In the first shutoff, power was cut to about 2 million people across northern and central California. In recent years, authorities have blamed electrical equipment for causing several deadly and destructive fires.

Weather conditions in Northern California eased Thursday evening, and PG&E said that it has restored electricity to 84 percent of the 179,000 customers who had their power shut off.

But forecasters say another wind event could be in store for Northern California on Saturday evening.