Ontario's police watchdog is looking into what led up to a rollover crash in Wellington County that ended in a trip to the hospital for a pair of suspected thieves who police say refused to stop their vehicle.

The OPP said the pursuit began on Sunday afternoon after a 31-year-old man and an 18-year-old woman had reportedly stolen fuel in Minto Township, about a 40 minute drive from Fergus. 

Police followed the suspect's vehicle until the 31-year-old driver lost control on Third Line near Mount Forest and rolled his vehicle into a ditch. 

The 31-year-old driver of no fixed address and the 18-year-old Listowel woman riding shotgun were both taken to hospital with what police described as "undetermined injuries."

Ontario's Special Investigations Unit is now handling the case and, because of that, police said they would not be able to provide any further information.