A SigAlert was issued at the scene, near Sunland Boulevard, and the lane closure is expected to last for about two hours, the California Highway Patrol said in a social media post shortly after 9:30 a.m.
The flames spread to a nearby embankment before being extinguished by responding firefighters.
Whether anyone was injured was unclear, and the cause of the fire was under investigation.
Westbound vehicles were at a standstill as the wreckage of the semitruck smoldered on the freeway shoulder. The traffic backup stretched several miles on the affected side of the interstate, while the eastbound lanes remained open.
Several westbound lanes were reopened by 1 p.m.
Shortly before 11 a.m., a separate crash involving two other big rigs also occurred on the westbound 210 Freeway, in nearby La Crescenta, according to a CHP incident log.
One person was transported to a hospital in unknown condition, according to the Los Angeles County Fire Department.
The second incident prompted the shutdown of all westbound lanes at that scene.