Oneida Nation of the Thames Police responded to a report of an injured male on a roadway at 10:30 p.m. on Friday in Southwold, Ont.
After an investigation, police learned a vehicle travelling westbound on Oneida Road from Ball Park Road rolled over numerous times after leaving the roadway.
The driver was then ejected from the vehicle during the rollovers.
Paramedics transported the 28-year-old Oneida man to hospital where he remains in critical condition.
OPP’s technical collision investigators and Oneida Nation of the Thames Police are looking into the cause of the crash.