(CNN) -- Cell phone video recorded from inside a car clipped by a FedEx tractor-trailer truck before it slammed into a bus carrying students in Northern California is being reviewed by investigators, the National Transportation Safety Board said Sunday.
The driver of the Nissan Altima that passed the bus just before the crash reported seeing flames coming from underneath the FedEx truck, but investigators have found no physical evidence of a fire before the collision, said Mark Rosekind, an NTSB board member.
The truck clipped the car occupied by Joe and Bonnie Duran before it crashed into the bus Thursday evening, killing 10 people -- five high school students, three chaperones and the drivers of both vehicles. More than 30 people, mostly teenagers, were taken to local hospitals.
Bonnie Duran told the CNN affiliate KOVR the truck was on fire before it hit the bus. She said she made a quick decision to swerve to avoid a direct hit from the truck, sending their rental car into a ditch. The video captured from inside the Durans' vehicle is being examined for clues, Rosekind said.
Despite the initial lack of physical evidence of a fire before the crash, "nothing is ruled out yet," Rosekind told reporters at a news conference Sunday.
The NTSB team is looking at the FedEx driver's last 72 hours to determine whether he had enough rest and whether he was using his cell phone when he lost control of his truck, Rosekind said. "Fatigue, distraction and other human performance issues are at the top of our list."
Dash-camera video from the first California Highway Patrol vehicle on the scene could also help investigators understand what happened in the minutes after the crash as both vehicles burned, he said.
Investigators are interested in knowing whether passengers on the bus, which was new, were wearing seat belts, Rosekind said. Some bus passengers were ejected from the vehicle, including the ones who died, he said.
The investigation shows the southbound truck did not brake as it crossed the median at a 10-degree angle and entered the northbound lanes, Rosekind said Saturday. Investigators found 175 feet of tire marks left by the bus, indicating the driver tried to avoid crashing into the truck.
A computer on the truck that could have revealed how fast the truck was traveling -- known a the electrical control module -- was destroyed by fire, he said. The electrical control module on the bus survived but has not yet been examined, he said.
Blood samples should be obtained from the bodies of both drivers, which will provide information about whether drugs or alcohol might have been in their systems, he said. Blood samples also might tell investigators if the drivers inhaled smoke from the fire, he said.
Investigators are only collecting information now and aren't drawing conclusions about the cause of the accident, Rosekind said.
Students traveling from the L.A. area
The students were traveling from the Los Angeles area to take part in a program at Humboldt State University, which allows prospective attendees to visit the campus.
Their journey ended in the fiery wreck 90 miles north of Sacramento when the truck hit one of three buses taking the teens to the campus in Arcarta.
The students on the buses represented 31 Southern California high schools. They were heading to "Spring Preview Plus," which invites low-income and first-generation prospective students to the university.
As part of the program, students stay in residence halls, attend events and visit with staff and students from a program that helps historically underrepresented students, the university said.
The two other buses in the caravan made it to the university. Those students were placed in dorms, and the university is offering them counseling.