RCMP said the collision occurred in the southbound lanes of Highway 2, north of Emerson Trail near Highway 672. Both lanes of the highway were shut down for hours but have since reopened.
Photos from the scene showed dozens of smashed cars and injured passengers. Witness Pancho Driedger said he drove up on the accident scene shortly after it happened.
"I saw a bunch of, at least 40 vehicles just scattered across the road and into the ditches and lots of screaming," he said. "There was this young girl sitting on her moms lap and just bleeding really badly. She passed out a couple times. I went and put my jacket over her just to make sure she was warm."
SEMS treated 29 patients, Alberta Health Services told CTV News Edmonton. Twenty-six of them were taken to hospital: six in non-life threatening condition and 20 with minor injuries.
A 16-year-old woman was among the injured and was transported to hospital in critical condition by STARS Air Ambulance. Her condition has since been upgraded to stable, according to RCMP.
Police say weather and road conditions were factors in the collision as thick, heavy fog reduced visibility along icy roadways. Investigators are working to determine if speed was also a factor.
Driedger said others were in the ditch, injured and cold, and called the entire ordeal "traumatizing."
Shortly after 12:30 p.m. local time, Grande Prairie RCMP said Highway 2 reopened to traffic in all directions and that emergency crews were no longer on scene.
"RCMP continue to investigate this collision," Mounties said in a news release. No charges have been laid.
Grande Prairie, a community of around 63,000 people, is roughly 390 kilometres northwest of Edmonton.
511 Alberta said the crash occurred on Highway 2 at Highway 672 north of the city Wednesday morning. 2
UPDATE #2: Grande Prairie RCMP say five people were taken to hospital with serious injuries after a Wednesday morning crash on Highway 2 involving 16 vehicles. Others were treated on scene for minor injuries.
Police say an initial investigation has shown that fog and icy roads played a part in the crash. Speed is also being looked at as a possible factor. They say they are continuing to investigate and no charges have been laid at this time.
Alberta 511 says all lanes of Highway 2 are blocked due to the crash at Highway 2 and Highway 672. Police are urging motorists to avoid the area, or, if they have to, use the Emerson Trail detour.
At the time of the collision, there was thick, heavy fog which caused reduced visibility and icy roadways, police said in the release. Speed is also being investigated as a factor.
STARS has been called to the scene. More information will be released on MyGrandePrairieNow.com as it becomes available.