According to the California Highway Patrol, only the slow lane and Citrus Avenue off-ramp were blocked as of about 5:30 a.m.
Crews are working to clear the accident. Traffic on the freeway is expected to be heavy until about 8 a.m.
The crash happened shortly before 3:30 a.m. The big rig ran into Cal Trans attenuators. The truck was also loaded with 4,300 pounds of material. It was not immediately clear what type of material it was transporting.
All lanes were closed for nearly an hour. At one point, traffic was reported to be at a near stand-still, with cars moving at 4 mph. The westbound 60 and westbound 210 are suggested alternates.
A cause for the accident was not immediately clear.