The charter bus carrying about 40 people lost control around 10:30 a.m. on the snow- and ice-covered lanes of Interstate 84, according to the Oregon State Police.
The bus came to rest at the bottom of a snowy slope. More than a dozen rescue workers descended the hill and used ropes to help retrieve people from the wreckage in freezing weather. The bus driver was among the survivors, but had not yet spoken to police because of the severity of the injuries the driver had suffered.
Lt. Greg Hastings said the accident happened west end of the Blue Mountains, and west of an area called "Deadman Pass." Stretches of highway in the rural and agricultural area of east Oregon tend to be icy in winter months.
I-84 is a major east-west highway through Oregon that follows the Columbia River Gorge.
Umatilla County Emergency Manager Jack Remillard said the bus was owned by Mi Joo travel in Vancouver, B.C., and state police the bus was en route from Las Vegas to Vancouver.
A woman who answered the phone at a listing for the company also confirmed with The Associated Press that it owned the bus and said it was on a tour of the Western U.S. She declined to give her name.
The bus crash was the second fatal accident in Oregon on Sunday morning. A 69-year-old man died in a rollover accident.
A spokesman for the American Bus Association said buses carry more than 700 million passengers a year in the United States.
"The industry as a whole is a very safe industry," said Dan Ronan of the Washington, D.C., group. "There are only a handful of accidents every year. Comparatively speaking, we're the safest form of surface transportation."