The incident happened just before 2 p.m. Monday near the Drum Forebay Road off-ramp.
CHP says the crash involves at least two big rigs and four to five other vehicles. It says several people have been injured, but their conditions are unknown at this time.
Video from above shows one of the big rigs off the road and down an embankment.
CHP says there's also a significant diesel leak because of the crash.
The cause of the crash is under investigation.
There's no word on when the freeway will fully reopen.
Stay with ABC7 News for the latest details on this developing story.