A tour bus has crashed into a ditch on the 401 between Brockville and Prescott sending 24 people to hospital .

OPP say four people suffered life-threatening injuries in the crash.

Twenty passengers have non life-threatening injuries and have been transported to hospital, including the driver.

OPP add they believe the reason for the numerous injuries was because the bus struck a rock wall as it crashed into the ditch, but the investigation is ongoing.

Initial reports say it was apparently a tourist bus. There were 37 passengers on board including a tour guide. The remaining 13 passengers were taken by bus to an unknown location. All of the passengers were visiting from China.

Leeds and Grenville Paramedics say multiple patients were without vital signs.

Brockville General Hospital says they have five patients in critical condition and said one other patient was being sent to a hospital in Kingston, Ont., by air ambulance.

We have received 5 patients as a result of the #Hwy401 accident near @TownofPrescott, each are in critical condition. We have a Mandarin translator onsite to support them. Another patient is being sent to @KingstonHSC via @Ornge — Brockville General (@BrockvilleGener) June 4, 2018

“All of the people that we have received are all Mandarin speaking,”‘ said Brockville hospital spokeswoman Abby McIntyre. “What I’ve been advised is that we have received five of the most critical.”

McIntyre said others injured in the crash are believed to be “walking wounded” who’ve been taken to other hospitals.

“Our teams are working hard with the folks that we’ve received and there’s all hands on deck for the moment,” she said. The hospital said it had a Mandarin translator on site to support the patients.

The Ottawa Hospital says they are treating three patients from the crash, one is in critical condition while 2 are in serious but stable condition.

“My understanding is they are tourists, there was a tour guide with them,” Const. Suzanne Runciman said of those on board, adding that they were non-English speakers.

Aidan Liang, the manager at operator Union Tour Express said the group was midway through a regularly scheduled route that began in Washington, D.C. The trip, which was set to include a stop in Toronto, was meant to end on Friday.

The Massachusetts based company caters mostly to Chinese visitors during the summer tourist season. Liang said he had not been in touch with the travellers families, or with local authorities in Ontario.

Maclean’s magazine reports the Federal Motor Carrier Safety Administration’s most recent data reported no crashes involving Union Tour Express vehicles, but a March 18 inspection of a bus with the same licence plate as the vehicle that crashed on the 401 reported “No Or Defective Bus Emergency Exits.”

The Chinese Embassy in Ottawa said in a tweet Monday evening it was aware of the collision and “very much concerned about the conditions of the injured passengers.”

“We are contacting the Canadian side for more information,” it said.

OPP are still investigating the cause of the crash.

A truck driver who passed by shortly after the crash said he could see passengers standing outside the bus holding bloody noses and some appeared to have facial injuries.

The bus was sitting in the ditch, up against some rocks, he said. A dash cam photo of the scene that he shared shows at least three ambulances and first responders, with about half a dozen people standing at the side of the road.

“It definitely looked very surreal and chaotic,” said the man who would only give his name as Robert. “OPP officers were assisting those who could get off the bus and to waiting ambulances. You could definitely see heavy damage to the front of the bus, including the passenger side of the front window.”

A tow truck driver Steve Rainey drove past the crash shortly after it happened and told CityNews it appeared the front window had been smashed out. He added It looked like one of the fender skirts was laying against the rock cut. He said there were multiple people scurrying around the scene.

Rainey said there had been reports of heavy rain in the area, but said it wasn’t raining when he went by the crash site.

The federal Transport Minister Marc Garneau has issued a statement saying they are monitoring the situation.

“Our thoughts are with all those affected by this accident. Our Government remains committed to the safety of Canadians on our roads and across the country. We are actively monitoring the situation as it continues to evolve.”

PC Leader Doug Ford, NDP leader Andrea Horwath and Premier Kathleen Wynne have commented on the crash, thanking the first responders who are on the scene.

Terrible news coming out of Eastern Ontario near Prescott. Thinking of all those involved in the accident. Thank you to the emergency responders who are on scene now. Our prayers are with you. — Doug Ford (@fordnation) June 4, 2018

My heart is with all those on the bus that crashed on the 401 near Prescott. We're all holding our breath, waiting for news. Thank you to first responders, and to medical personnel helping the victims. — Andrea Horwath (@AndreaHorwath) June 4, 2018

I just heard about the bus crash near Prescott. As we wait to hear more about the situation, our thoughts are with everyone hurt in the crash, and the first responders who rushed to the scene to help. — Kathleen Wynne (@Kathleen_Wynne) June 4, 2018

The eastbound lanes on Highway 401 are closed in the area.

UPDATE ROAD CLOSURE: #Hwy401 WB west of #Prescott – All WB lanes closed at Edward St (Prescott) due to collision, Emergency Services on scene. ^lm pic.twitter.com/mVsdWLZo34 — OPPCommunicationsER (@OPP_COMM_ER) June 4, 2018

With files from The Canadian Press