An eight-year-old student has died after a school bus crashed on a busy freeway in Calgary's southwest at the height of the Thursday morning rush period.

The school bus involved in the crash Thursday morning struck a gravel truck parked on the side of the road.
(CBC)

The girl was found unconscious and wedged face down between two seats. Rescuers said she suffered major blood loss.

A 13-year-old boy who was in critical condition with "full systems injuries" was upgraded to stable, according to an update by the Alberta Children's Hospital Thursday afternoon.

Two students who were in serious condition and seven students with minor injuries have been released from hospital.

A paramedic treats one of the injured students on scene.
(CBC)

Police said it appears the short yellow school bus struck a gravel truck parked on the shoulder of busy Crowchild Trail near 17th Avenue Southwest and then continued on to smash into a light standard. Both drivers were unhurt.

"The initial collision with the dump truck actually peeled off a part of the side of this school bus," Calgary police Insp. Roger Chaffin told CBC Newsworld. "It caused a considerable amount of damage."

The side of the bus was sheared off and the front end crumpled. A witness told CBC News that the female bus driver was "hysterical."

A total of 11 children ranging in age from eight to 17 were on the bus, which appeared to be equipped with seatbelts, but it's unclear if they were wearing them.

Several people driving by stopped to help, including an off-duty firefighter and a doctor.

"The one little girl that was in there, in between the seats, we didn't see her right away," said witness Tom Taylor. 

"And then I just climbed into the bus and then I saw her and called the doctor and switched spots with him and let him look after her."

Eleven students were on the bus when it crashed.
(CBC)

Six students were on the way to The Third Academy, a private special education school, and five attend Mountain View Academy, another private school that shares the same building.

"We're all a big family in that school so if something bad happens to one, it happens to all of us," said Mountain View vice-principal Colleen Ryan, as she waited at the hospital with parents.

"So our thoughts right now are with the children and that's what we need to be focusing on."

The speed limit on the stretch of road where the crash happened is about 70 km/h.

"It's a fairly good straightaway at that point," said Chaffin. "The weather today is very clear. There's no unusual road conditions."

Investigators have determined the gravel truck was parked on the side of the road because of mechanical issues.

Police are interviewing the bus driver, who is employed by The Third Academy, and will look at what factors led to the collision.

Investigators said she is suffering from "emotional trauma."