The driver of the truck lost control and hit the median around 4 a.m. At one point, part of truck caught on fire, and 40 to 50 gallons of diesel fuel spilled onto the freeway.
The driver, who is OK, got out of the car and tried to extinguish the flames.
Commuters were being diverted off the freeway at Irwindale Avenue. Officials said the eastbound lanes would be shut down until at least 8 a.m.