Grey Bruce OPP are investigating a collision on Highway 21 near Jackson between an SUV and a farm tractor.
Police say it happened on May 20th just after 8 p.m. when a 42 year old driver of a Grey Westbound SUV rear-ended the farm tractor being driven by a 52 year old.
They say officers arrived to find the SUV with extensive damage in the middle of the highway.
According to police, four people were transported by ambulance to hospital and treated for minor injuries.
Police say they're still investigating the circumstances surrounding the collision and no charges have been laid at this time.