San Bernardino , California ( CNN ) -- A deadly tour bus crash in the Southern California mountains left at least eight people dead and dozens injured Sunday , officials said . The difficult terrain hampered rescue efforts in San Bernardino County , east of Los Angeles , as authorities tried to extricate some of the victims . Though the early death toll stood at eight , that number is expected to rise , California Highway Patrol Officer Mario Lopez said . Authorities believe the bus rear-ended a sedan , crashed with a pickup truck pulling a trailer and rolled over about 6:30 p.m. ( 9:30 p.m . ET ) . The incident took place in a mountainous area of State Route 38 , between Mentone and Forest Falls , San Bernardino Fire Department spokesman Eric Sherwin said . At least 42 people suffered injuries ranging from minor to severe , he said . A parade of ambulances snaked down a narrow , sloping highway Sunday night , waiting to transport the dozens injured . The highway was reduced to one lane for both inbound and outbound ambulances , which had to contend with a downhill grade and winding roads . By late Sunday night , all passengers had been removed from the bus , Sherwin said . The cause of the crash was not immediately known . Lopez identified the bus company as Scapadas Magicas of National City , California . The company did not immediately return a request for comment early Monday . Federal safety records indicate Scapadas Magicas had no reported crashes in the two-year reporting period leading up to Sunday . The company received a `` satisfactory '' rating in a safety review last month . Investigators pored over the debris with flashlights overnight and Monday morning , searching for clues . But evidence of a rollover seemed abundantly clear : The top of the bus over the driver 's seat was caved in , and part of the roof was ripped open . CNN 's Holly Yan and Emily Smith contributed to this report .
NEW : Authorities investigate the bus crash ; its records show it 's ` ` satisfactory '' A patrol officer says he expects the death toll to rise . At least 42 are dead from the crash in San Bernardino County . Cars take turns on one lane of a mountainous road .