The blaze occurred along the eastbound lanes of the freeway at about noon.
The Los Angeles County Fire Dept. declared the accident a hazardous-materials situation at 12:23 p.m. The tractor-trailer was hauling gasoline.
The California Highway Patrol closed all lanes of the 60 Freeway in both directions between the 710 and 605 freeways. Connector lanes to and from the 710 Freeway were also closed. The Paramount Blvd. overpass was also closed to traffic due to structural concerns.
Officials on Wednesday night said they'd need to inspect the affected stretch of the freeway and overpass in order to determine when they'd reopen the freeway.
As of 11 p.m., the roadway was still smoldering as Caltrans crews continued to work at the scene.
Firefighters used chemical foam to spray the burning tanker. The fire flared up several times after momentarily abating.
About 200 firefighters from several agencies, including Los Angeles County, Montebello, Monterey Park, Santa Fe Springs and Vernon, were on scene.
Officials from the Montebello Fire Dept. and California Highway Patrol held a news conference at 2:30 p.m.
A passing motorist called 911 to report the tanker fire, officials said.
The vehicle is a double-tanker truck. The rear trailer caught fire but appeared to have been extinguished by 3 p.m. Officials said the tractor-trailer cab and the front trailer had burned to the ground, and firefighters were concentrated on the rear tanker. According to fire officials, there were 8,800 gallons of gas in the tankers.
The tankers were hauling gasoline. They were both reportedly full.
The driver and one passenger exited the burning vehicle and escaped without injuries. It was previously reported a third person was in the vehicle.
One firefighter was injured fighting the fire, suffering a fractured leg. That firefighter was treated at a hospital and released.
The sudden severity of the fire forced the occupants to abandon the vehicle as soon as possible, without pulling to the shoulder or driving to an off-ramp. The truck came to a stop in the 3 and 4 lanes, the two farthest on the righthand side.
An explosion that was heard was believed to be from exploding concrete from the Paramount Blvd. bridge due to extreme heat.
Officials said environmental issues were a concern due to a mixture of chemicals and water used on the fire running into storm drains. The Dept. of Fish and Game was on scene to help coordinate the environmental response.
The cause of the fire was under investigation. It was not immediately known if there was a traffic incident with another vehicle. The truck was the only vehicle on fire.
The trucking company was assisting in the cleanup and investigation.
Motorists were advised to avoid traffic in the San Gabriel Valley altogether if possible Wednesday.
Area motorists were advised by the CHP to plan for alternate routes for Thursday morning commutes. CHP also said motorists should plan for the possibility of a long-term closure at the scene.