Authorities say the fire erupted while the tractor-trailer was in the far-right eastbound lane at Hacienda Boulevard at 2:50 p.m. The truck was hauling cylinders of compressed hydrogen, which is flammable and potentially explosive. Los Angeles County Fire Inspector Scott Miller said the driver got out of the cab safely.
L.A. County Fire Inspector Tony Akins said the fire began in the tractor of the 18-wheeler and then spread to the trailer.
"The safest way to deal with that product at this point is to continue to let those burn off," Akins said. "Hydrogen burns an invisible flame. You will see flickers of red and blue."
Residents in the area were ordered to "shelter in place." Firefighters doused the flames, but the fire destroyed the truck cab. Crews backed off and were pouring streams of water on the hydrogen tanks to cool them down.
The cause of the fire was under investigation.
All lanes of the freeway were shut down as a precaution. Eastbound lanes were closed at the 605 Freeway. Westbound lanes were closed at Azusa Avenue before they were re-opened shortly after 8 p.m.
All but one eastbound lane of the freeway reopened around 10 p.m., according to the California Highway Patrol. Around 11:30 p.m., the CHP said all lanes and ramps reopened.