The National Transportation Safety Board is investigating Thursday's crash between a FedEx Freight truck and a motor coach on Interstate 5 in northern California that left 10 people dead.
According to news accounts, the double-trailer rig lost control after switching lanes and veered across the median directly into the path of a northbound charter bus operated by Silverado Stages. The bus was carrying high school students to Humboldt State University for an event.
NTSB officials said investigators are looking at all possible causes, including human factors such as fatigue. Both drivers were among the dead.
In a statement, FedEx Chairman and Chief Executive Officer Frederick Smith expressed his "deepest personal sympathies and the condolences of over 300,000 other FedEx team members to everyone involved in this accident, including the families of the students and others who lost their lives and those who were injured and the families and friends of the FedEx Freight driver who died in the crash.
"It will take some time to fully understand exactly how this accident occurred and why. In the meantime, I want everyone to know that we at FedEx are committed to providing every resource necessary to assist investigators in their efforts to understand what happened.
"Just as important, we are committed to providing support for our team members, their families and the families of all of those who lost their lives. This is a tragic day for these families, and our thoughts and prayers are with them."
Read more about the FedEx Freight truck crash from the LA Times