Some lanes reopened after fiery big rig crash on 405 Freeway near Mulholland Drive

A dump truck filled with concrete caught fire after crashing Monday afternoon, shutting down all but one lane of the 405 Freeway near Mulholland Drive and snarling traffic just before the rush-hour commute, officials said.

A Sigalert was issued after all southbound lanes, along with all but one northbound lane, were shut down. By 5:30 p.m., several lanes, including three southbound lanes and one more northbound lane, were reopened, according to the California Highway Patrol.

Dramatic video captured the aftermath of the collision, with about a dozen bystanders swarming the fiery wreckage to rescue at least one trapped person.

The Good Samaritans, some dressed in military uniforms, pulled one person to safety before Los Angeles firefighters arrived. Others appeared to try to put out flames with bottled water and debris.

Fire crews extinguished the blaze and were treating three patients. Two were critically injured, and a third was in fair condition, the Fire Department said.

The collision occurred just before 3 p.m. on the northbound side, CHP Officer Elizabeth Kravig said. Crews were working to clear concrete debris strewn across freeway lanes.

alene.tchekmedyian@latimes.com

Twitter: @AleneTchek

UPDATES:

5:35 p.m.: This article was updated to reflect some lanes have been reopened.

4:45 p.m.: This article was updated with more information about the crash and rescue efforts.

This article was originally published at 4 p.m.