(KTLA) — The intensity of a brush fire near Castaic, California, was captured on KTLA video Wednesday afternoon when a series of “fire tornadoes” or “fire whirls” were spotted.

The fire tornadoes developed around 3:20 p.m. as crews worked to contain the Route Fire, which had forced evacuations and the complete closure of the 5 Freeway.

The largest appeared to reach 20 feet in height.

The U.S. Forest Service defines a “fire whirl” as a “spinning vortex column of ascending hot air and gases rising from a fire and carrying aloft smoke, debris, and flame.”

They can range in size from less than 1 foot to more than 500 feet in diameter.

The Route Fire was initially reported around noon Wednesday near northbound lanes of the 5 Freeway, according to the Angeles National Forest.

Eight firefighters suffered heat-related injuries as crews struggled to contain the fire in 100-degree temperatures amid a heat wave that has developed over much of Southern California.

KTLA captured footage of a much larger fire tornado on Aug. 10 during the Sam Fire in northwestern Los Angeles County.