PRESCOTT, Ontario — A bus ran off the road and smashed into a ditch in eastern Ontario on Monday, sending at least 24 people to the hospital, four with life-threatening injuries, provincial police said.

Constable Suzanne Runciman said the bus was carrying approximately 37 people, including the driver and a tour guide, when it went off the westbound lanes of Highway 401.

"My understanding is they are tourists. There was a tour guide with them," Runciman said, adding that they were non-English speakers.

An official at one hospital said the patients brought there spoke Chinese.

A manager at Massachusetts-based Union Tour Express said he had heard that one of the company's buses was involved in an accident, but did not have any further information.

A truck driver who passed by shortly after the crash said he saw people standing outside the bus holding bloody noses and some appeared to have other facial injuries. The bus was sitting in the ditch, up against some rocks, he said.

The Ornge air ambulance service said at least one person was flown for treatment in Ottawa, which is about 55 miles from the accident scene.

Brockville General Hospital in Prescott, near the crash, said it received five patients who all required critical care and said one other patient was sent to a hospital in Kingston, Ontario, by air ambulance.

"All of the people that we have received are all Mandarin speaking," spokeswoman Abby McIntyre said.

McIntyre said other people injured in the crash were believed to be "walking wounded" who were taken to other hospitals.