Authorities said a multi-vehicle accident caused the tanker driver to lose control of the truck. The truck hit the freeway's center divider on the eastbound side, near the Corona (71) Expressway, at about 10:30 a.m.
The California Highway Patrol says it was a chain-reaction crash, started when the driver of a semi-truck merged into a blue Mitsubushi sedan, forcing it into the side wall. Then the driver of the semi-truck swerved the other way, toward the tanker truck. The tanker lost control and slammed into the center divider.
That caused another car to fly over the center divider into westbound lanes. Two other cars also crashed.
The tanker-truck driver managed to get out safely. No injuries were reported.
CHP dispatcher Jon Twenty said about six cars were involved in the wreck and some of them were also burned.
Firefighters allowed the tanker truck to burn itself out. The tanker truck was carrying almost 9,000 gallons of fuel. It took several hours for the fire to burn itself out. All that remained was the charred, blackened chassis and tires.
The accident shut down all lanes of the freeway, and eastbound traffic was diverted into Corona at Green River Road, causing a major traffic jam.
All westbound lanes of the 91 had been opened by 3 p.m.
Temporary repairs were made Friday night, and by 10:30 p.m., all eastbound lanes had been opened.
"If there is any hazardous materials, it will have to be cleaned up, and by all means, Caltrans will do a structural damage assessment on the actual freeway and if any repairs are needed, then they'll be doing that," said CHP Officer Maurice Walker early Friday afternoon.
"I was about three cars back, so all I saw was [the tanker] sliding across, hit the center, went airborne and burst into flames," said Brandon Leger, a witness to the scene. "It was unreal, it was like life was in slow motion watching it."
"We could see the flames from almost a mile back and it looked like we were driving into this giant cloud of black smoke," said motorist Lori McLean.
"I asked this gentleman from the police department, 'Did the driver get out?' He said, 'Yeah, that's him right over there.' I said, OK. The rest doesn't matter," said driver Steve Thompson.
City News Service and The Associated Press contributed to this story.