Seven people were riding in the cab of a pickup truck when it hit the rear of a backhoe and flipped. (CBC)

Members of the Blood Tribe in southern Alberta are mourning the death of five people — including three children — in a highway crash involving a truck that carried seven people in its cab.

The RCMP corrected their initial report Wednesday evening that two children and three adults had died, pointing to the difficulty emergency crews had in getting access to the wreckage of the badly damaged pickup truck.

Seven people were riding in the cab of the truck on Highway 810 near the village of Glenwood, north of Cardston, on Wednesday afternoon when it crashed into the rear of a backhoe.

Both vehicles, which were travelling southbound, overturned and fell into the ditch.

'It's going to be a community effort in regards to try to lessen the sorrow and the pain that I can't imagine that the family is going through.'—Blood Tribe Chief Charles Weasel Head

The driver of the pickup, James Well, 28, was pronounced dead at the scene, police said Thursday.

His three children — Reese, 9, Jenna, 6, and Jordan, 1 — were killed in the collision.

Passenger Clement Wolf Plume, 47, also died. His two sons, aged 15 and 16, were taken to Cardston Hospital with minor injuries. They have been released.

The driver of the backhoe was taken to the hospital with injuries that were not life-threatening.

At least one child's car seat was found at the scene, but only one person was wearing a seatbelt, said police.

The RCMP said at least one child's car seat was found at the scene of the crash. Three children between the ages of one and nine died, along with two adults. (CBC)

The road was clear and dry at the time of the crash. Investigators are looking into whether speed or alcohol were factors in the collision.

"It's going to be a community effort in regards to try to lessen the sorrow and the pain that I can't imagine that the family is going through," said Blood Tribe Chief Charles Weasel Head, who was attending the annual general meeting of the Assembly of First Nations in Calgary.

"We're a very large-populated community, but we're a very engaged, connected community, and whenever there's a loss of one of our members, everybody takes it very personal."

He called the victims in the accident "very personable individuals" but declined to speak further out of respect for the deceased.

Cardston is about 230 kilometres south of Calgary.