National Transportation Safety Board officials investigating the deadly collision of a FedEx truck and a tour bus filled with high school students in Northern California will examine two new pieces of video evidence.

One is cellphone video shot by the driver of a Nissan Altima hit by the truck before it slammed into the bus. The other is footage from a dashboard camera provided by the California Highway Patrol.

"This is critical information for us to understand how the fire progressed and also how the passengers exited," said Mark Rosekind, a member of the NTSB.

More clues may also be available from a black box-type recorder on the bus that collects vehicle data. The FedEx truck also was equipped with a recorder, but it was destroyed in the fire.

"Nothing is ruled out yet," Rosekind said. "We're giving you what we know."

On Sunday, Rosekind provided more information on the driver of the twin-trailer FedEx truck, whom he did not identify. The driver was based in Sacramento and earlier on the day of the accident had taken a load of freight to a town about 50 miles south of the Oregon border. The driver picked up two semi-trailers -- one partly loaded, the other empty -- and was returning to Sacramento when the accident occurred.

Rosekind said the NTSB was in the process of learning the exact nature of the contents being hauled to determine if the truck was carrying any hazardous material. He said investigators also would look at possible driver "fatigue, distraction and other human performance issues."

"We're going to go over that driver's last 72 hours at least," Rosekind said, noting that investigators would be looking at cellphone use, for example.

Both witnesses said the truck veered sharply from southbound lanes, across the median and into a Silverado Stages charter bus, which carried 48 people, including 44 Southern California high school students. The students were headed to Humboldt State University for an orientation program.

"When they collided, it was boom!" said Ryan Householder, 31, who watched from his home.

Rosekind said the truck left no skid marks on either the roadway or the median as it veered into oncoming traffic. In contrast, more than 145 feet of tire marks indicated that the bus driver tried to stop and swerved to the right. Both drivers were killed.

Five students and three adult chaperones were also killed.

Rosekind said investigators are expected to remain on the scene for five to 10 days.