The Green Fire stands at 21 acres burned and is 20% contained, according to Cal Fire. Evacuation warnings remain in place and Palisades Drive remains closed, the Corona Police Department said in a social media post around 11:17 p.m.
The blaze was reported at 4:20 p.m. on the eastbound side of the 91 Freeway, possibly in a homeless encampment between the freeway and Palisades Drive, according to the Riverside County Fire Department.
The agency said multiple engine crews from the county and Corona Fire Department converged on the location a short time later, encountering flames moving at a moderate rate to the southeast.
Five Cal Fire air tankers and three water-dropping helicopters initiated runs by 5:30 p.m., significantly slowing the blaze as it approached several properties on Nutmeg Drive. Firefighters set up a defensive perimeter that prevented damage to the homes.
By 6 p.m., all air tankers and two helicopters had departed the location, with ground crews using surrounding roads to strengthen and secure containment lines, according to reports from the scene.
As winds died down toward sunset, firefighters were making steady progress encircling the brusher, though they were expected to remain on the fire lines into Saturday morning.
There were no reports of any injuries.
No further details were immediately known. The cause of the fire is under investigation.
City News Service contributed to this report.