A spokesman for Nipawin Royal Canadian Mounted Police told reporters RCMP was conducting a rescue operation together with multiple emergency personnel some 19 miles north of Tisdale.
"We can confirm there are fatalities among the passengers on the bus. There are also a number of serious injuries. We cannot confirm numbers at this time," he said.
The Saskatchewan Junior Hockey League (SJHL) said on Twitter it was aware of an accident involving the bus of the Humboldt Broncos team.
Nipawin Hawks, who were scheduled to play against them on Friday night, said on Facebook that the game had been cancelled.
Saskatchewan Premier Scott Moe expressed his condolences in a Facebook posting and thanked first responders for their courageous response "under the most difficult circumstances imaginable."