Smoke from the so-called Border 2 Fire, which was blowing west and southwest in the direction of Otay Mesa, was visible for miles, reports NBC 7’s Todd Strain. A large vegetation fire began burning Thursday afternoon on a hilltop near the U.S.-Mexico border. As night fell, the flames cast an eerie glow across Otay Mountain.

A wildfire is spreading through the Otay Mountain Wilderness near the U.S.-Mexico border. Southern California is under a red flag warning for critical fire risk through Friday.

A new wildfire spread quickly on Thursday in Southern California near the U.S.-Mexico border, The blaze is in the Otay Mountain Wilderness, home to the endangered Quino checkerspot butterfly and other unique species.

It was first reported just after 11 p.m. near northbound lanes of the freeway in Sherman Oaks, according to the Los Angeles Fire Department.

Watch Duty, a nonprofit that tracks wildfires, said that as of 11:26 p.m. the fire was estimated to be 10 acres, burning in heavy brush east of the freeway in the Sepulveda Pass. By about 12:23 it had grown to 20 acres, though fire crews were making good progress on the blaze, Watch Duty reported.

A new fire broke out Wednesday night along the 405 Freeway in the Sepulveda Pass. The fire was burning on the east side of the 405 near the Sepulveda Fire Road. Winds were at about 5 mph, according to the Los Angeles Fire Department.