At least 15 people have died after a truck collided with a bus carrying senior citizens in a rural portion of Canada’s Manitoba province on Thursday afternoon, according to local authorities.

The bus was headed south on Highway 5 toward a casino near the town of Carberry, while the semitrailer was headed east on Highway 1, Royal Canadian Mounted Police officer Rob Lasson said in a news conference.

The semitrailer struck the bus at the intersection of the two highways north of Carberry, roughly 170 kilometers (105 miles) west of Winnipeg.

“Immediately it became apparent that this was a mass casualty situation,” Lasson said.

In addition to the 15 killed, 10 others have been taken to a hospital, authorities said. The injured being treated included the drivers of the semitrailer and the bus, Lasson said.

Twelve ambulances responded to the collision scene, as well as an air ambulance, said Jennifer Cumpsty, executive director of Acute Health Services.

Manitoba has not seen a mass casualty traffic accident like this before, Lasson told reporters.

“This is new for us and our investigators, and it is very emotionally draining for them as well,” he said.

A majority of those on the bus were seniors who lived in and around the city of Dauphin, according to RCMP assistant commissioner Rob Hill.

Not all of the victims’ families had been notified as of Thursday evening.

Flags have been lowered in mourning at Manitoba’s legislative building, and Prime Minister Justin Trudeau marked the tragedy in a statement on Twitter.

“The news from Carberry, Manitoba is incredibly tragic. 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,” Trudeau tweeted.

William Doherty, CEO of shipping company Day & Ross, which operated the semitrailer, has promised full cooperation with the investigation, noting that “at this time, we have limited details from the scene.” (CNN)

•PHOTO: First responders are pictured following the deadly road accident near Carberry, Canada, on Thursday. Nirmesh Vadera/AFP/Getty Images

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