Federal investigators say they haven't found any physical evidence that a FedEx truck was on fire before it slammed into a bus carrying high school students, killing 10 people in Northern California.
National Transportation Safety Board member Mark Rosekind said Sunday that investigators are not ruling out a pre-impact fire, but they did not find any physical evidence at the crash scene.
Investigators said Saturday they were looking into a driver's claim that the FedEx tractor-trailer was already on fire when it careened out of control across a freeway median on Interstate 5 in Glenn County.
The bus was carrying Southern California high school students to a campus tour of Humboldt State University.
Five students, three adult chaperones and both drivers died in Thursday's collision in Orland, a small city about 100 miles north of Sacramento.