Forty-three people have been injured, several critically, in a tour bus crash on the Coquihalla Highway, 30 kilometres south of Merritt, B.C.

Police initially said the tour bus was heading from the Okanagan Valley to the Vancouver area when it appears to have hit a median and flipped.

An RCMP crash analyst says the bus driver was passing a commercial vehicle, when the bus strayed into the soft earth of the median. The driver then steered hard, causing the bus to flip.

'They were so scared. There were children and lots of screaming and crying. - Eyewitness Sue Gordon

RCMP initially said everyone on the bus sustained some kind of injury, but the Interior Health Authority reported late Thursday only 43 of the 54 passengers had gone to hospital.

An air ambulance was called for five of the passengers who were airlifted to hospital in critical condition, according to the Interior Health Authority.

Health officials say 10 passengers were seriously injured, suffering broken bones and compound fractures. Twenty-eight passengers had more minor injuries in the form of cuts, scrapes and bruises.

RCMP Sgt. Norm Flemming said the cause of the single vehicle accident is under investigation.

Chaos at accident scene

Sue Gordon, who was on her way home to Tsawwassen, says she knew something was wrong when police drove by her with lights flashing and sirens blaring.

"Within about three minutes I came upon a stop, a standstill and there it was," she told CBC News. "About 20 cars ahead there was a bus on the road with its windows blown out and people were everywhere."

Ambulances cut through traffic that's gridlocked on Highway 5 northbound just north of the Coldwater Interchange on Thursday (Aug. 28). (Emily Wessel/Merritt Herald)

Gordon says she was about two car-lengths away from where all the people were lying down being treated when she got out of her car to assess the delay.

"They were being treated by bystanders, really. One ambulance was on scene, but in the meantime 14 showed up.”

Gordon says it was a chaotic scene. People were frightened.

“They were so scared. There were children and lots of screaming and crying. It was horrific ... just awful to see and I felt awful because I couldn’t really do anything," she said.

"There were paper towels covered in blood blowing around. Garments that had fallen out the windows were strewn along the side ... glass everywhere."

"The people were really being taken care of exceptionally well by so many bystanders. A few of the cars right near the front had a couple of doctors. Two of them were ER doctors which is always amazing to come upon in situation like that.”

"When the ambulances arrived, they had loads of blankets to cover the victims. Some were sitting up in shock. Some were laying down, in gurneys. They were calling anyone with muscles near the accident scene to help lift people on to gurneys. An air ambulance hovers over the scene of a tour bus crash on the Coquihalla Highway, 30 kilometres south of Merritt. (Submitted by Sue Gordon)

B.C. Ambulance sent 19 ground ambulances to the scene along with six helicopters.

Twenty-two patients were sent to Kelowna General Hospital, 10 were sent to Royal Inland Hospital in Kamloops and 11 patients were sent to the Nicola Valley Hospital in Merritt said Interior Health in a statement.

All three hospitals initiated a Code Orange response to bring in extra staff and resources to support the influx of patients.

Four hours after the accident, Interior Health spokeswoman Michaela Swan told CBC News patients were still being removed from the scene.

Tour bus passengers visiting from Asia

Nick Kam, director of service for Super Vacation, a company based in Richmond, B.C., that identifies itself on its website as the largest "Chinese tour operator in North America," confirmed the bus was on a tour organized by his company.

"It's our tour, yes," Kam said.

Kam said the bus was not owned by his company but was chartered through another company. He also said that company provided the driver.

A Super Vacation employee told CBC News the passengers came from Hong Kong, China, Taiwan and other locations. She said the tourists had left Vancouver Aug. 25 on a trip to the Rocky Mountains and were returning to Vancouver

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

Daniel Parsons was on his way home from work when he happened upon the scene. Police and ambulances were already there and two school buses had been brought in to help with the injured.

"You could see the bus, it was right off the side of the highway and it looked like it had rolled over," Parsons said.

"There was just a pile of people all along the side of the bus receiving medical assistance and you could see some blood on the side of the bus. It was a pretty bad scene for sure. I haven't seen one like that."

He said the crash appeared to happen along a slight curve in the highway.

The highway was closed Thursday night in both directions with air ambulances landing on the roadway. The northbound lanes which were closed for helicopter landings were quickly re-opened.