Three people were taken to hospital with one person suffering lifethreatening injuries.
The cause of a single-vehicle crash in Chatham-Kent is under investigation.
Police say it happened on Highway 40 near Bush Line around 7 a.m. Friday when a vehicle left the roadway before coming to rest in a nearby ditch.
Three people were taken to hospital with one person suffering life-threatening injuries, according to police.
Anyone who may have witnessed the crash is asked to contact police or Crime Stoppers anonymously.