A 67-year-old woman from Riverside, a 73-year-old woman from Pasadena and a 23-year-old woman from Mexico were killed when a charter bus rolled down a rain-slicked embankment in North San Diego County, according to the California Highway Patrol.
The bus, which is owned by a company based in El Monte, had 18 other occupants who suffered varying levels of injuries, the CHP said. Eleven of the surviving passengers suffered injuries described as "serious" by the agency.
The El Monte-based company that owned the charter bus involved in the crash is Executive Lines Incorporated, the CHP said. The company told NBCLA that they were open as of Sunday morning and still taking passengers.
The bus started in El Monte on Saturday morning and was making pickups throughout Riverside County before the crash, the CHP said. The final destination of the bus was Tijuana.
The bus was on Interstate 15 in Pala Mesa on Saturday when it swerved, rolled down an embankment and landed on its roof, North County Fire Protection District spokesman John Choi said.
Several passengers were thrown from the bus, and one of the dead was trapped under the vehicle after it landed on its roof shortly after 10 a.m. Saturday off Interstate 15, the CHP said.
One man, Christopher Williams, said he was driving from Rancho Cucamonga when he saw the bus flip. He jumped out of his car to help and carried several people up the hill to safety.
"It looked like the bus driver was trying to turn the wheel and he hit the embankment," said Williams. "The bus ended up flipping over."
The CHP said the bus driver is a 52-year-old man from Whittier who suffered from minor injuries. The CHP said he is cooperating in the investigation.
The CHP said the bus had seat belts but not all were being used at the time of the crash.
The investigation into the cause of the crash is ongoing and the bus is being inspected. Officials told the Associated Press that federal investigators are sending a team to investigate the crash.
The Associated Press contributed to this report.