The four passengers who were killed Wednesday when their bus rolled over as it tried to avoid steel pipes that had spilled onto Interstate 10 near Arizona were from Southern California, officials said.

Riverside County coroner's officials identified the passengers as Jessica Garcia, 30, of Chula Vista; Luz Rivera, 44, of Compton; Angel Hernandez 49, of Hacienda Heights; and 67-year-old Pablo Ramirez of Pico Rivera.

The crash occurred after a big rig jackknifed on Interstate 10 in Blythe about 2:15 a.m. when its driver reportedly tried to pass a slower vehicle and struck a center divider, causing a load of steel pipes to spill on the highway and into incoming traffic.

That set off a chain reaction of crashes that led to the bus rolling off the freeway shoulder, resulting in dozens injured and the four deaths.

The bus had departed about 5:45 p.m. Tuesday from El Paso and had been expected to arrive at 6:45 a.m. in Los Angeles.

The driver of the bus, which is part of a fleet of vehicles operated by El Paso-Los Angeles Limousine Express Inc., was unable to stop and safely exit the freeway to avoid the crash, the company's president, Jerry Rosenbaum, said in a statement. The driver, who is from the Los Angeles region, was a "little bit banged up," he told The Times.

"No one has made any allegations about the bus’s maintenance or the bus driver’s actions being contributing factors of this accident," he said.

The low-cost transportation company has been operating across the Southwest since 1966 and is in the top third of its class of transportation companies when it comes to its driving, safety and inspection records, according to the Department of Transportation

"Our No. 1 concern is the passengers and taking care of their immediate needs," Rosenbaum said.

The California Highway Patrol continued to investigate the crash Wednesday.