A debris fire alongside Interstate 15 in El Cerrito Monday snarled traffic on the busy corridor but burned itself out before firefighters arrived.
The non-injury blaze was reported at 3:25 p.m. on southbound I-15, near Ontario Avenue, according to the California Highway Patrol.
The agency said cardboard boxes and other materials caught fire, burning on the right shoulder and later spilling over into the slow lane.
All traffic lanes were impacted until an unidentified motorist in a pickup truck jumped out and kicked the burning debris back out of lanes, the CHP said.
A Riverside County Fire Department engine crew was sent to the location, but by the time firefighters arrived, the blaze had burned out, and there were no visible flames, according to reports from the scene.
There was no word regarding how the fire might have started.