EDMONTON -- Three people are dead after a tour bus rollover at the Columbia Icefield near Jasper, Alta. on Saturday, according to RCMP.

Several RCMP detachments, including Jasper, Banff and Lake Louise, and three STARS helicopters responded to the scene of the rollover, where multiple victims were found in critical and serious conditions, according to Kerry Williamson with Alberta Health Services.

RCMP said there were 27 passengers on the vehicle at the time of the rollover.

Helicopters were needed to reach the injured from the rollover site before STARS could transport them to hospital according to RCMP.

STARS officials confirmed they took three patients to hospitals in Edmonton and Calgary. A 27-year-old woman was transported to Edmonton's Royal Alexandra Hospital in serious but stable condition, a 31-year-old man was taken to the Univeristy of Alberta hospital in critical, potentially life-threatening condition and a middle-aged woman with critical, potentially life-threatening injuries was taken to the Foothills Medical Centre in Calgary.

In total, 14 people suffered critical, life-threatening injuries, four were in serious but stable condition and six were in stable condition according to Alberta Health Services. 

Eyewitnesses on social media said the bus was travelling on the Athabasca Glacier when it rolled over.

Ice Explorers are buses equipped with monster-truck tires regularly take tourists on off-road trips up to the Athabasca Glacier.

According to another witness on Twitter, a rockslide caused the rollover.

RCMP said due to the remote location and the number of injured, emergency staff from several surrounding areas was called in.

Alberta Health Services confirmed that medical crews from Jasper, Banff, Nordegg, Rocky Mountain House, Canmore, Sundre, Calgary and Edmonton responded, plus air ambulances from Slave Lake, Lac La Biche and Edmonton and a chartered helicopter out of Canmore. 

CTV News received a statement from Banff Jasper Collection by Pursuit, the company that operates the Ice Explorer tours.

“Our immediate concern is with the injured and their families and we are supporting the efforts of first responders.”

The icefield is located about 100 kilometres south of Jasper and is one of the largest non-polar icefields in the world.

Jasper RCMP is investigating the cause of the rollover. Highway 93 is open at this time.

With files from The Canadian Press