Two of three children are well enough to leave hospital following last week's school bus crash in southern Alberta.

Crossfield Mayor Nathan Anderson said Monday the pair are doing so well they may even be home already.

The third child, a five-year-old boy, is also continuing to improve.

"There's been a slight improvement today — only slight — but at least it's improvement," Anderson said.

He added that the boy's vital signs are stable and doctors are keeping him sedated so his body can heal.

"He could have taken a turn for the worse. He was kind of in that precarious space and, rather, he's taken a slight turn for the better."

The three were rushed to hospital in Calgary with critical injuries after the bus collided Friday with a large pickup truck at a rural intersection near the town.

The front end of the bus was crushed and it ended up against a guard rail in a ditch.

Six other children and the female bus driver also went to hospital with less serious injuries. The truck driver received minor wounds and did not need medical treatment.

RCMP continue to investigate the cause of the accident.