The accident was first reported shortly after 6 a.m. near the 405 Freeway interchange.
Traffic was crawling through just one open lane as emergency personnel investigated the scene. Traffic on the northbound 101 Freeway was backed up all the way to the 170 Freeway.
A car was seen off the side of the freeway in the bushes.
Details on injuries or the cause of the accident were not immediately available.