Investigators from the National Transportation Safety Board say they expect their "Go Team" to be in the Northstate for one to two weeks. The team will be gathering facts about the fiery crash between a FedEx Truck and a charter bus carrying prospective college students that left 10 dead and dozens injured.

In a news conference Friday afternoon, NTSB officials said their investigation is "not just about the what, but about the why."

They also said they need to discover why the crash happened so that they can issue any safety recommendations that could prevent future crashes.

"Our mission is to determine why this crash happened," said an NTSB official Mark Rosekind.

Rosekind also said the NTSB will "investigate whether a median barrier was necessary" as part of their inquiry.

The NTSB said it was too early to determine why the semi-truck crossed the median and it's unknown if sufficient remains are available to conduct a toxicology report

They are asking anyone who believes they may have witnessed the crash, or seen something before the crash that may have led to what happened, to contact either local law enforcement, or the NTSB by sending an email to witness@NTSB.gov.