Rob Hill, Commanding Officer of the Manitoba Royal Canadian Mounted Police, said the bus was carrying 25 people in Manitoba and authorities are deploying all their resources in the province to the scene.
Ten people were taken to hospitals.
TV broadcasters aired images of what looked like a large van or bus smoldering in a ditch near a transport truck with a smashed engine on a road.
The pavement was littered with debris – broken glass, a large bumper and what looked like a walking aid.
Seven blue and yellow tarps were stretched out.
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Ambulance helicopters have been dispatched to the scene from Winnipeg and Regina.
“The news from Carberry, Manitoba is incredibly tragic,” Canadian Prime Minister Justin Trudeau tweeted.
“I’m sending my deepest condolences to those who lost loved ones today, and I’m keeping the injured in my thoughts. I cannot imagine the pain those affected are feeling – but Canadians are here for you.”
Carberry is 170 kilometres west of Manitoba’s capital of Winnipeg.