RCMP say the chain-reaction crash happened Wednesday afternoon.
Initial reports indicate a semi collided with the back end of a utility trailer being towed by a pickup truck.
An SUV travelling beside the semi as crushed between the semi and its trailer, and the female driver was taken to hospital in critical condition.
Another pickup truck was then struck, with its driver taken to hospital as a precaution.
A fifth vehicle got tangled in the debris but that driver was released on scene.
The drivers of the semi and the first pickup involved were taken to hospital but only as a precaution.
The semi truck was designed to carry ammonium nitrate but was empty at the time of the crash.