Police officials say the bus was on a return trip from Las Vegas, Nevada to Vancouver when it slid through a guardrail and fell down a steep embankment over the weekend.
The crash along Interstate 84 in eastern Oregon killed nine people on board and injured about 20 others.
"I've been a firefighter for 20 years, and this is the first time I've ever seen anything like this," said Lieutenant Steven Brost, with the Pendleton Fire and Ambulance.
Lt. Brost was one of the first responders who helped to treat dozens of injured passengers.
Some of the survivors are expected to resume their journey to Vancouver Wednesday. According to the Red Cross, a number of the passengers are afraid to get aboard another bus.
As a result, a car dealer in La Grande, Oregon is offering to drive them back using SUV's and other passenger vehicles.
At least 14 of the crash victims are still in hospital.
With files from CNN