"The vehicle made a hard turn to the left and then right, causing it to lose control and enter the meridian between the highway and the weigh scale," said Sgt. Jeff Campbell.

There were varying reports initially as to how many people were ejected from the vehicle but after further investigation, Campbell said five people were thrown from the van, in total.

Two people were pronounced dead on scene: a man and woman, both in their 30s.

RCMP investigate the site of the single-vehicle rollover that killed 2 people and seriously injured 5 others. (Dave Gilson/CBC)

The female driver of the van and a male front-seat passenger were both trapped in the vehicle and had to be extricated, according to police.

That passenger was then transported to hospital by ground ambulance in life-threatening condition, while the driver was flown by helicopter to hospital in Calgary in critical, life-threatening condition.

The other three injured passengers were listed in serious condition and taken to hospital by ground ambulance.

Campbell said everyone in the van was from Morley, which is part of the Stoney Nakoda First Nation.

Krista Hunter, whose niece was among the injured, says the crash is devastating for the entire Stoney Nakoda First Nation. (Dave Gilson/CBC)

Krista Hunter, whose niece was among the injured, said both of the deceased had children, and news of the crash has been "devastating" to the community of roughly 3,000 people.

"Not only for the seven families but for the whole community, it's shocking," she said. "It's scary when you lose young people like this."

"We're trying to find ways to come together and cope with it," Hunter added. "But in our culture, we believe the creator is here and looking after the families."

with files from Dave Gilson