Firefighters from across the Bay Area headed to northern Nevada to help battle the rapidly growing Hawk Fire, a wind-driven wildfire that has forced tens of thousands of residents to flee their homes.

Crews from Oakland, San Francisco, Hayward and Fremont left early Sunday as part of a mutual aid response to support firefighters already on the front lines near Reno.

The fire grew significantly overnight amid strong winds and dangerous fire conditions, prompting Nevada officials to request additional assistance from neighboring states.

"We're all trained to the same levels," said San Francisco Fire Department Captain Mariano Elias. "The beauty of our mutual aid system in California is we can work together. We have the same radio channels, we can speak to each other and have the same training."

Nevada Gov. Joe Lombardo has declared a state of emergency as firefighters work to contain the blaze.

RELATED: Fast-growing Hawk Fire grows to 13,000 acres near Reno; 42,000 people forced to evacuate

More than 1,000 firefighters and emergency personnel have been deployed to battle the fire under challenging conditions that include heavy smoke, strong winds and red flag warnings.

"The fire was going up and over fire trucks, fire personnel and law enforcement personnel," Washoe County Sheriff Darin Balaam said during a briefing.

According to the Washoe County Sheriff's Office, approximately 90,000 people have been affected by the fire. More than 42,000 residents have been ordered to evacuate as flames continue to threaten communities in the region.

Among those displaced is Jessica McClain, who evacuated her Somerset home Saturday night.

"I never thought in a million years I'd have to evacuate," McClain said. "I'm sleeping in my car at a gas station."

She described the experience as surreal and said she grabbed family keepsakes before leaving.

"You never think it's going to be you," McClain said. "I loaded up all my photo albums from my parents and family."

Finding shelter has also been difficult.

"I called 20 hotels," she said. "All the hotels were booked within the entire city of Reno."

Fire officials announced Sunday that investigators have determined the Hawk Fire was caused by human activity, though the exact cause remains under investigation.

"We can confirm the fire was human-caused," an official said during a fire briefing. "It is still undergoing active investigation."

Officials have not released additional information about how the fire started. Fire crews continue working to protect homes and slow the fire's advance as dangerous weather conditions persist across the region.

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