They were identified as Yongho Lee, 75, of Lynnwood, Oun Hong Jung, 67, of South Korea and his wife, Joong Wha Kim, 63.
Authorities said an 11-year-old girl from South Korea was among those killed.
Oregon State Police officials identified the girl Wednesday as Youmin Kim, who was visiting relatives in British Columbia before the nine-day bus tour of the western United States.
Authorities earlier said 57-year-old Dale Osborn of Spanaway died in the crash.
The crash occurred as the bus was returning to Vancouver, B.C., on the final leg of the vacation tour.
Vice Consul Chul Ho Choi, who went to Pendleton, Ore., from Seattle to help authorities with translations and to notify relatives, said five of the victims were South Korean citizens.
Another 38 people were injured, including driver Haeng Kyu Hwang, 54, of Vancouver, B.C.
At least 10 people remained hospitalized Wednesday afternoon at facilities stretching from Boise, Idaho, to Portland, Ore.
State troopers have been going to hospitals with photographs of unclaimed property, including purses and luggage, in an effort to return items found at the scene.
The cause of the crash has yet to be released, and police have said it could take a month or more to determine whether the driver was at fault.
The investigative team includes police and three National Transportation Safety Board inspectors.
The crash occurred near a spot on the interstate called Deadman Pass, at the top of a steep, 7-mile descent from the Blue Mountains. There were icy spots, but nothing unusual for this time of year.
"The crash happened on a pretty straight stretch before they headed down the hill," said Tom Strandberg, a spokesman for the Oregon Department of Transportation.
The posted speed limit is 55 mph for trucks and buses and 65 mph for cars. Drivers, however, are required to go slower in treacherous conditions.
Despite its foreboding name -- coined in pioneer times long before the automobile -- the pass had not been deadly in the 21st century.
In the past 10 years, there had been 59 accidents, but no deaths, on that stretch of highway, Strandberg said.
Transportation Department records show Sunday's crash to be the state's deadliest since a two-car collision in Portland killed nine in October 1971.
Six years before that, a Greyhound bus lost control on an icy section of I-5 in southwest Oregon.
The Christmas Eve crash killed 14 people.
More Northwest Headlines
With protest over, Shell prepares for Arctic Ocean drilling Lawsuit over lease for Shell Arctic drilling fleet rejected Higher wages a surprising success for Seattle restaurant Court denies Medina millionaire’s release from Montana jail Prosecutors charge man in fatal Bonney Lake crash Woman, 87, goes missing while picking berries in Skamania County New wildfire burns at least 8 structures in Mason County Judge tosses lawsuit seeking Kurt Cobain death-scene photos
Our new comment system is not supported in IE 7. Please upgrade your browser here.