Emergency crews and medical staff were still reeling Friday after a massive pileup Thursday near Edmonton sent about 100 people to hospital.

An initial crash between a bus, tractor trailers and several other vehicles triggered a domino effect that resulted in a chaotic jumble of vehicles that had spun-out, crashed or wound up stranded in snow banks alongside the QEII highway approximately 65 kilometres south of Edmonton. Police confirmed more than 100 vehicles were involved.

A spring snowstorm was in full swing in the region and the highway was snow-covered when the pileup occurred.

"It was a pretty massive pileup, far bigger than I've ever seen before. From what I could see there were remarkably few injuries considering the scope of the accident," said Derek Fildebrandt, who witnessed the crash while riding in one of the buses.

Officers from a number of detachments were called to the scene to help sort out the accident along with members of the Edmonton Police Service.

Alberta Health Services communications staff initially tweeted that 300 "minor to moderate injuries" had been reported.

Later, the number of minor injuries was revised to about 100 after crews on the scene further assessed the situation.

Those injured in the crash -- including a number of passengers on three Greyhound buses -- were sent to hospitals in Edmonton, Red Deer, Leduc, St. Albert, Fort Saskatchewan, Devon, Wetaskiwin, Stony Plain, Lamont and Camrose.

AHS said one person with serious injuries was sent to the University of Alberta hospital in critical condition. RCMP said the adult male was located under a tractor trailer and appeared to have been hit after getting out of his vehicle.

Three other people with moderate injuries were taken to hospitals in Wetaskiwin, Devon, and Leduc.

"This is the worst I've ever seen," said tow truck driver Dorothy Curtis. "Carnage, complete carnage. It's a very bad day for a lot of people today."

A tractor trailer carrying 74 head of cattle was also involved in the accident, but all but two of the animals were safely transferred to a Live Stock Emergency Trailer -- one of seven located throughout Alberta to rescue livestock that become stranded in crashes or breakdowns.

The highway, which serves as the main artery between Edmonton and Calgary, was closed in both directions after the collision, with traffic detoured to other routes in the area. By late Thursday evening, the accident had been cleared up and the highway was once again open.

Although the investigation was still ongoing Thursday, police said speed was likely a factor.

In a separate incident, three people were killed in a collision about 85 kilometres north of Westlock, Alta. Thursday on Highway 44. Police said a northbound pickup truck collided head-on with a southbound compact car. Three passengers in the car were killed, while two others were seriously injured.

The driver of the truck was seriously injured and was taken to hospital.