Driver Killed in Gasoline Truck Explosion : Accident: The tanker-trailer falls from a connector span onto the river bottom and explodes. Northbound lanes on the Ventura Freeway are closed for hours.

A jackknifed tanker truck loaded with gasoline exploded into a massive fireball late Saturday morning, killing its 23-year-old driver and sending a huge column of noxious gray smoke that closed northbound lanes on the Ventura Freeway for more than three hours.

The truck’s cab flipped upside-down about 11:20 a.m. as the driver, who was headed onto the Ventura Freeway from California 33, rounded a curve on the raised freeway connector near the Ventura River.

When the truck rolled, the tanker-trailer--filled with more than 8,000 gallons of gasoline--flipped over the metal railing, plunged onto the dry Ventura River bottom and exploded into flames.

The truck and tanker burned for about an hour, igniting a small brush fire in the dry riverbed.

The blaze charred the entire cab, which was still on the roadway, as well as burning about 120 feet of railing along the elevated roadway that connects California 33 and the northbound Ventura Freeway near downtown Ventura. The accident closed the highway connector all day, forcing motorists to detour off California 33 onto Ventura surface streets at Stanley Avenue.

A hazardous-materials team from the Oxnard Fire Department spent much of the afternoon testing the smoldering ground around the accident site and found that a large amount of fuel remained, said Capt. Mike O’Malia, who heads the team.

“There is definitely some soil contamination,” O’Malia said. “But just how much and what should be done to clean it up is yet to be determined.”

Officials from the state Department of Fish and Game and the Ventura County Environmental Health Division will look at the site over the next few days and decide whether the contaminated river-bottom soil should be removed before rains wash the material into the river and out to sea, O’Malia said.

The driver, Carlos Humberto Alonzo of Oxnard, was burned beyond recognition in the accident. He was identified with the help of a gasoline sales slip recovered from the cab.

Alonzo had just loaded the Atlas Bulk Carriers tanker with fuel in Ventura and was headed to Goleta, said Adrian Delhierro, the weekend manager in Atlas’ Oxnard office.

A veteran driver with the company, Alonzo had operated big rigs since he was 16 years old, Delhierro said. He is survived by his wife and two children.

Witnesses said the deafening explosion rocked their cars and shot flames hundreds of feet into the air and out across two lanes of traffic on the northbound Ventura Freeway.

“It was just a huge ball of orange flames,” said 42-year-old Greg Jex of Murietta, who was driving north on the Ventura Freeway with his wife and two daughters. “We didn’t see it flip over but we saw the explosions. There must have been like three or four explosions in all.”

Jex and his wife, Teri, 35, said they could feel intense heat from the blaze more than 100 yards away.

“It was like a volcano,” Teri Jex said. “It looked like flames were erupting from under the freeway.”

Fire crews wearing silver heat-retardant suits and oxygen masks battled the blaze while onlookers covered their mouths with T-shirts to protect themselves from the choking smoke.

The heat from the inferno warped the metal railing and gutted the 40-foot trailer.

Witnesses said a few drivers drove past the burning rig immediately after the accident.

“It was crazy,” said an emotional Renee Ledwell, 31, of Santa Maria, who was headed home after taking an exam at Ventura College. “People were just driving right through the flames.”

Although several people driving northbound on the Ventura Freeway saw the explosion, California Highway Patrol officers were still looking for anyone who might have seen how the accident occurred, CHP Officer Dave Cockrill said.

The accident backed up Ventura Freeway traffic for several miles, as CHP officers diverted traffic onto northbound California 33 or to surface streets in Ventura. Cars snaked through the city trying to get back on the freeway using the one open lane of the Main Street bridge over the Ventura River, which was damaged in the March floods.

An alternative route would have been California 150, which runs from Ojai to Carpinteria, but it remains closed from last winter’s heavy storms.

This is the fourth time this year that either the north or southbound lanes or all lanes of the Ventura Freeway have been closed to traffic between Ventura and Santa Barbara. Three years ago, the stretch of freeway was closed for nearly a week after a Southern Pacific freight train carrying hazardous materials derailed near Seacliff.

Saturday, after California Department of Transportation engineers checked the safety of the bridge, a single northbound lane was opened to traffic about 2 p.m., and the second northbound lane was opened about 5 p.m. As of 10 p.m., the connector remained closed as investigators tried to determine the cause of the accident.

Times staff writer Kenneth R. Weiss contributed to this report.