YUCAIPA, Calif.—A company linked to a tour bus involved in a crash in Southern California that killed at least eight people failed more than a third of federal vehicle safety inspections in the past two years, records obtained Monday show.

The cause of the Sunday crash east of Los Angeles remained under investigation. Dozens of people were injured.

The crash left State Route 38 littered with body parts and debris, and the bus sideways across both lanes with its windows blown out, front end crushed and part of the roof peeled back like a tin can.