A brush fire burning in the Cajon Pass prompted a SigAlert along the highway Wednesday afternoon, officials said.

The Bronco Fire had burned about 20 acres, according to the San Bernardino County Fire Department, though by about 5:30 p.m., that number had been updated to under 100 acres and 20% containment.

The No. 3, 4 and 5 lanes of the 15 Freeway were shut down beginning at Kenwood Avenue, according to the California HIghway Patrol.

It is unknown how long the closure will last, but authorities asked motorists to expect “heavy delays.”

By 2:10 p.m. there were no visible flames and firefighters were mopping up in the fire as Sky5 was overhead.

The blaze comes as intense heat bakes the Southland and increases fire danger.

A Flex Alert has was issued in California urging residents to conserve energy amid high temperatures.