San Bernardino County fire spokesman Eric Sherwin says the bus overturned at about 6:30 p.m. Sunday night near the San Bernardino National forest.
The northbound SR 38 was closed while crews worked at the scene.
Authorities said all 43 people involved in the crash sustained some kind of injury. At least 15 people were critically hurt. The injuries of those transported to hospitals ranged from life-threatening to minor.
Victims have been transported to multiple area hospitals. At least four adults and two children were taken to Loma Linda University Medical Center and two others were sent to Arrowhead Regional Medical Center. Redlands Community Hospital took in two patients and two others were expected.
The bus, apparently based out of Tijuana, and two other vehicles collided around 6:30 p.m. on the mountain highway north of Yucaipa and below Forest Falls, according to the San Bernardino County Fire Department.
Initial reports said the bus first struck a pickup truck and then a sedan. The cause of the accident was unclear, but officials said the bus' brakes and speed may have been a factor.
San Bernardino County fire spokesman Eric Sherwin said he did not know where the bus was going, but Highway 38 leads to Big Bear, a popular recreation area. The Mexican consulate was at the scene of the crash.
ABC News: http://abclocal.go.com/kabc/story?section=news/local/inland_empire&id=8979373