Police east of Edmonton were busy Wednesday morning, after dozens of vehicles were involved in a highway crash.

Late Wednesday morning, Strathcona County RCMP said officers, along with the County’s emergency crews were on the scene of a massive crash on Highway 21 near Township Road 510 in southern Strathcona County.

A number of drivers told CTV News that fog in the area at the time of the crash made driving nearly impossible, and many were travelling at slow speeds before the collisions occurred.

“It was zero, the car to truck that I hit was four feet ahead of me, and I couldn’t see them unti9l three feet and I was only going, my odometer was below 50 [kilometres an hour],” Mark Klotz said.

“I was doing about, maybe 60 kilometres [an hour] and all of a sudden I run across this big tractor trailer across the highway,” Doug Froelick said. “I swerved and I just missed it by maybe half a foot and down in the ditch I went.”

Others said the fog was so thick they couldn’t see what was happening, even as they heard other collisions nearby.

“While we were out helping there were some crashes behind us which is rather unnerving, so you hear those noises in the fog and you don’t know what’s happening behind you,” Larry Gibson said.

According to RCMP, the crash happened at about 9:30 a.m. – and involved about 100 vehicles in total, approximately 30 to 40 vehicles were so damaged they had to be towed from the scene.

Sections of Highway 21 in both directions were closed for several hours Wednesday.

Officials on the scene said four people had to be taken to hospital, the most serious injury was a broken leg – any other injuries are minor.

RCMP said visibility in the area is at zero, due to heavy fog – police believe reduced visibility because of the fog contributed to the crash, but investigators haven’t determined the initial cause.

Drivers were advised to avoid the affected area; the scene was cleared and opened to traffic by mid-afternoon.

With files from Breanna Karstens-Smith