LOS ANGELES (AP) — A fast-growing brush fire has forced thousands of people to evacuate in a mountainous area north of Los Angeles.

The Canyon Fire erupted Thursday afternoon, expanding rapidly to over 7.6 square miles (19.7 square kilometers) by 11 p.m., as reported by the Ventura County Fire Department. More than 400 personnel, along with multiple planes and helicopters, were engaged in combating the blaze, which remained uncontained late into Thursday. Officials noted its eastward spread into Los Angeles County.

The fire is currently burning just south of Lake Piru, a reservoir within the Los Padres National Forest. It’s near Lake Castaic, a well-known recreational spot that the Hughes Fire affected in January. That previous fire consumed about 15 square miles (39 square kilometers) in just six hours, prompting evacuation orders or warnings for 50,000 people.

Friday was expected to bring sunny, hot, and dry weather to the area affected by the Canyon Fire, with temperatures likely reaching close to 100 degrees Fahrenheit (38 degrees Celsius) and minimum humidity levels dropping to the mid-teens, according to the National Weather Service. Winds were anticipated to start light in the morning but increase from the south to southwest by afternoon.

In LA County, approximately 2,700 residents evacuated late Thursday, with 700 structures under an evacuation order, officials reported. An additional 14,000 residents, along with 5,000 structures, were under an evacuation warning. The regions within the Val Verde zone transitioned from an order to a warning status.

Nearby Ventura County’s evacuation zones were mostly unpopulated, according to Ventura County Fire Department spokesperson Andrew Dowd on Thursday. Fifty-six individuals were evacuated from the Lake Piru recreation area.

Dowd called the blaze a “very dynamic situation” caused by hot, dry weather, steep and rugged terrain and dry fuel.

LA County Supervisor Kathryn Barger, who represents the district, urged residents to evacuate.

Barger emphasized the hazardous conditions brought by the extreme heat and low humidity in the north county, which can cause the flames to spread rapidly. “If first responders instruct you to evacuate, do so without hesitation,” Barger stated.

The new blaze comes as a massive wildfire in Central California became the state’s largest blaze of the year, threatening hundreds of homes and burning out of control in the Los Padres National Forest.

The Gifford Fire had spread to 155 square miles (402 square kilometers) by Thursday night with 15% containment. It grew out of at least four smaller fires that erupted Aug. 1 along State Route 166, forcing closures in both directions east of Santa Maria, a city of about 110,000 people. It has injured at least four people. The causes of the fires are under investigation.

Wildfire risk will be elevated through the weekend across much of inland California as a heat wave gripping the area intensifies. August and September are typically the most dangerous months for wildfires in the state.