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Roadside ignition was source of Springs Fire: Officials

David Mcnew / Getty Images

Firefighters battle a growing wildfire that reached the beaches in Ventura County and pushes its way toward the upscale city of Malibu.

An undetermined roadside ignition in grass and debris off the Ventura Freeway in Southern California sparked the Springs Fire, officials said on Sunday.

Officials are calling it an "undetermined roadside ignition of grass and debris" that started the region's largest wildfire so far this year that scorched nearly 44 acres along the Ventura and Los Angeles county lines.

Now that firefighters have the Springs Fire nearly under control after three days fighting in steep, rugged and rocky terrain, the focus of the blaze turns to a grassy area off the Ventura Freeway in the Conejo Grade where the fire was sparked on Thursday.

Full coverage from NBCLA: Southern California Wildfires

The fire began off the southbound side of the Ventura Freeway at Camarillo Springs Road. The fire quickly spread to over 28,000 acres of the Santa Monica Mountains in near triple-digit heat and low humidity.

Some 15 homes and several recreational vehicles were damaged and several communities in the path were evacuated. No injuries were reported and no one died.

The fire prompted a massive mutual-aid response from agencies across the state.

At one point, 9,000 firefighters — assisted by water-dropping and fire-retardant dropping planes and helicopters — attacked the flames.

The fire was 60 percent contained on Sunday, officials said.