PENDLETON, Ore. -- Investigators in Oregon are trying to piece together the final moments before a Vancouver-bound tour bus carrying 48 people careened down a steep hillside, ejecting some of the passengers and killing nine.

Police said Monday they still weren't sure how fast the bus was travelling before the crash on a partly icy highway in a rural mountain pass east of Pendleton.

The bus was carrying tourists, including some who had been living in Canada, on the final leg of a nine-day tour of the western United States.

Oregon State Police Lt. Gregg Hastings said it could take a month or more to determine whether the driver, a 54-year-old man from Vancouver, will face any charges.

State police confirmed 39 people were transported for treatment of injuries and at least 10 of them were treated and released.

Hastings told a news conference Monday that investigators were still trying to confirm the citizenship of the victims but a majority were of South Korean background and lived in British Columbia, Washington state, Oregon and even Idaho.

In some cases, he said, investigators have had to work with consular officials from Korea to determine where victims lived because Korean passports were the only available identification.

"We would like to express our heartfelt condolences and our hearts and prayers to the victims, their families and those in many communities in the United States, Canada, Korea, Taiwan and Japan," he said.

The names of the deceased would not be included in a list released by police, said Hastings, who noted the investigation could last at least four weeks.

The list named seven Canadian residents confirmed injured in the crash, including the driver, identified as Haeng Kyu Hwang. Two of those people were treated and released from hospital and police did not release the conditions of those still in hospital.

RCMP Sgt. Peter Thiessen said Oregon police have asked the Mounties to help notify relatives of the crash victims in the Vancouver area.

The bus was travelling westbound in the left lane of Interstate 84 when it hit a concrete barrier, veered across both westbound lanes and went through the guardrail before plunging about 60 metres down the embankment, Hastings said. The National Transportation Safety Board said the bus rolled at least once.

When the tour bus came to a rest, terrified passengers looked for their loved ones.

"People screamed and yelled," said Jaemin Seo, a 23-year-old student from Suwon, South Korea, who has been studying in Vancouver. "Some mothers screamed to find their son or daughter."

Seo said he was awakened by screaming and was ejected from a broken window as the bus careened down the hill. He suffered a broken ankle, a gash in his arm and shallow scratches across his face.

Police have not released the names of the nine people who died. The survivors ranged in age from seven to 74.

The passengers were supposed to arrive Sunday night in Vancouver, where their journey began. Instead, they were taken by ambulance and aircraft to 10 hospitals across three states.

Amid the chaos, authorities struggled to identify some victims or locate their relatives, many of them living half a world away in South Korea. At least one survivor, a man in his early 20s, had yet to be identified.

The crash occurred near a spot on the interstate called Deadman Pass, at the top of a steep, 11-kilometre descent from the Blue Mountains. Though there were icy spots where the crash occurred, that was nothing unusual for this time of year, said Tom Strandberg, a spokesman for the Oregon Department of Transportation.

He said a sanding truck had applied sand a few hours earlier and was behind the bus making another run when the crash occurred. The sand truck driver was among the first at the scene.

Berlyn Sanderson, 22, of Surrey, B.C., said she also was thrown from the bus.

"It's kind of like one of those dreams you have of the world ending," Sanderson told reporters.

Rescuers faced the challenge of bringing survivors up a steep cliff, Pendleton fire Chief Gary Woodson said. They descended the hill and used ropes and baskets to help retrieve people from the wreckage in freezing weather.

Some survivors were carried on backboards by six or eight rescuers. Others were hoisted in baskets, and an all-terrain vehicle arrived toward the end of the operation, Woodson said.

The National Transportation Safety Board said two investigators were expected to arrive at the crash site. They will look into why the bus left the road, the condition of the road at the time, the condition of the guardrail, the actions of the driver, and the operations of the company that owns the bus, the agency said.

Yoo Byung Woo, a 25-year-old survivor, said it was snowing and foggy at the time. She told the Oregonian newspaper that one passenger was frightened and asked if they could take another route. Some passengers were dozing when the driver slammed on the brakes.

Yoo said rocks smashed through windows after the bus crashed through the guardrail and rolled down.

Umatilla County Emergency Manager Jack Remillard said the bus was owned by Mi Joo Tour & Travel in Vancouver. A bus safety website run by the U.S. Department of Transportation said Mi Joo has six buses, none of which have been involved in any accidents in the past two years.

A spokesman for the NTSB, Peter Knudson, said seatbelts aren't required on such buses. "We have been concerned about this for some time," Knudson said.

The Red Cross has been offering food, clothing and hotel arrangements for survivors as they are released from the hospital.

Jake Contor, a Pendleton resident who speaks Korean and helped translate for the Red Cross, said he had spoken with several survivors.

"The stories have been fairly consistent: braking, swerving, sliding on the ice, hitting the guardrail, then sliding down the embankment," Contor said.

He said the passengers told him the bus left Boise, Idaho, on Sunday morning and was supposed to arrive in Vancouver that night. The survivors who spoke to Contor were seated at the back of the bus and said it appeared that the front and centre of the coach sustained the most damage.

The interstate links Boise and Portland through the Blue Mountains and the Columbia Gorge.

With files from The Canadian Press