The RCMP says dashboard camera footage from a tractor-trailer which captured a tour bus rolling over on the Coquihalla Highway appears to show speed was not a factor in the crash.

The bus carrying 56 people hit a median on Thursday afternoon about 30 kilometres south of Merritt, B.C., then skidded across several lanes and rolled into a ditch ejecting numerous passengers before landing the right way up.

Coquihalla tour bus crash

An injured passenger is rushed to hospital following a tour bus crash Thursday afternoon on the Coquihalla Highway. (CBC)

Air and ground ambulances transported 43 people with the most serious injuries to nearby hospitals in Merritt, Kamloops and Kelowna. Patients were also taken to hospitals in Hope, and to the Royal Columbian Hospital in New Westminster.

Officials with the Interior Health authority said on Friday morning that seven passengers remain in critical condition, six are in serious condition, 11 are in non-life-threatening condition and 19 have been released from hospital.

An additional 12 passengers with less serious injuries were treated by the Fraser Health Authority, said the official. It was not clear if they had been released.

RCMP Sgt. Brian Nightingale said the dash-cam footage, captured by a truck travelling behind the bus, shows human error or mechanical failure, rather than speed, are the most likely causes.

"It's more an issue that the driver drove into the centre median and then veered too hard trying to get onto the road," Nightingale said.

"We're doing mechanical [inspections] today on the bus, so that will rule out any kind of mechanical factors, like steering and braking and that kind of stuff."

The footage has not been released by police.

Police have confirmed the road was bare and dry at the time and visibility was good.  No other vehicles were involved in the crash.

Many bus passengers from overseas

The passengers were on a tour organized by Super Vacation, a company based in Richmond, B.C., which leased the bus from Western Bus Lines.

Super Vacation company spokesman L. Lau said his company has been in touch with some of the patients, who are being treated at at least seven different hospitals, and has been figuring out ways to provide assistance.

"We have been planning for everything right now," said Lau, who declined to give his full name. "Of course, some of the patients we can't see."

The company has sent chartered buses to bring the passengers who are able to travel back to Vancouver.

The company, which describes itself as the largest Chinese tour operator in North America, has said many of the passengers are from mainland China, Hong Kong and Taiwan, though some are from B.C. and elsewhere in Canada.

Lau said it was their last day on the tour of the Rockies and there was nothing on the itinerary as they were returning to Vancouver, so there would be no reason for the bus to be rushing anywhere.

"We are waiting for the police report," Lau said.

He said the bus and driver belonged to Western Bus Lines, which he said is a "major local bus company with 35 years of experience."

Western Bus Lines, based in Kelowna, did not reply to repeated voice messages and emails.

Meanwhile, the crash has raised questions about the use of seat belts on buses. RCMP say numerous passengers were ejected from the vehicle when it rolled.

Questions raised over seat belts

A 2010 incident in which a van from the same company collided with an SUV also raised the issue of seat belts.

The SUV allegedly ran a stop sign striking a shuttle bus operated by Super Vacation and knocking it onto its side. There were 25 people on board.

The accident resulted in a dozen B.C. Supreme Court law suits from passengers against the tour company. Passengers sued for multiple injuries including fractures, contusions, and loss of consciousness.

The claims alleged the driver was operating the bus at an excessive rate of speed with defective or no seat belts.

The driver of the SUV responded by saying any injuries were the fault of Super Vacation failing to advise passengers to wear and properly adjust seat belts.

The tour company denied the claims and the case has yet to be heard in court.

While there is a requirement for the bus driver's position to have a seat belt, so he can maintain control during a crash, Transport Canada says there are currently no requirements in North America requiring seat belts for passengers on board newly built motor coaches.

The safety agency says the U.S. is preparing legislation that could require seat belts in motor coaches by 2016.

It says Canada is reviewing the proposed U.S. regulation to determine whether it would benefit Canadians.

Consulate confirms 2 from Taiwan

Abraham Lin, director of consular services for the Taipei Economic and Cultural Office in Vancouver, said his office had confirmed that two of the patients are Taiwanese nationals, a 20-year-old man and a 21-year-old woman.

"They are just studying for the summer and they joined the bus tour for the Rocky Mountains," Lin said.

Lin said his office had been in touch with one of the Taiwanese passengers and had contacted the other's parents in Taiwan.

Neither the Chinese Embassy in Ottawa nor the consulate in Vancouver could be immediately reached, but Super Vacation said the consul general of China in Vancouver was heading to Kelowna to provide assistance.

Photos from the scene on Thursday showed the white bus upright, with visible damage to its side and the Western Bus Lines logo mostly scraped off. Passengers and emergency workers could be seen standing alongside the bus, with debris strewn about the road.

With files from The Canadian Press