PORTLAND, Oregon (Reuters) - Five people were killed and at least 20 others injured on Sunday when a charter bus skidded off an icy highway near Pendleton, Oregon, police said.

The Oregon State Police said a preliminary investigation showed the charter bus, carrying about 40 people, "lost control on the snow/ice covered westbound lanes of Interstate 84" near Pendleton.

The bus crashed through a guardrail and went down an embankment of around two hundred feet. The rescue required personnel trained in rope rescue to bring people back up to the highway, police said.

By early afternoon 20 people had been taken to the hospital and other injured passengers were being taken to area hospitals.

There were three planes standing by at the Pendleton airport to transport the injured to hospitals out of the area. Pendleton is about 210 miles east of Portland, police said.

Authorities did not immediately release the name of the charter bus company, the destination or origin of the bus.

Pendleton is in northeast Oregon near the border with Washington state. (Reporting by Teresa Carson; Writing by Dan Whitcomb; Editing by Todd Eastham)