Three people were killed and several people were injured after a glacier tour bus in Canada rolled over at a national park on Saturday, according to officials.

The Royal Canadian Mounted Police (RCMP) said the glacier sightseeing bus rolled at one of the most popular attractions in the Rocky Mountains, the Columbia Icefield in Alberta’s Jasper National Park, early Saturday afternoon.

Alberta Health Services said on Twitter that a total of 24 patients were transported to hospitals in Edmonton, Grande Prairie, Hinton and Calgary after the “tragic accident.”

“Our thoughts and deepest sympathies are with the families and loved ones of the deceased, and with all of the patients impacted by this tragedy,” AHS tweeted.

Of those sent to hospitals, 14 were transported in critical, life-threatening conditions. The others were reported to be in stable condition.

Vanja Krtolica, who witnessed the incident, told the Globe and Mail newspaper that the rollover happened around 2 p.m. after the vehicle lost control as it drove down an access road.

“All of a sudden, everybody started screaming because they saw the coach lose control,” he told the paper. “It was careening down that 33 degree … steep hill and lost control.”

Tanya Otis with Pursuit, a company that runs the sightseeing tours of the Athabasca Glacier, told 360aproko News that one of its Ice Explorer off-road buses overturned en route to the glacier.

“We will provide additional details as they become available,” Otis said. “Our immediate concern is with the injured and their families and we are supporting the efforts of first responders.”

Alberta Premier Jason Kenney said he was “saddened” to hear of the accident and thanked emergency workers for responding.

“Prayers for all involved in the incident,” he tweeted.

RCMP told 360aproko News they are investigating the cause of the rollover with the support of a collision analyst.