UPDATE: Central Region OPP report Highway 11 northbound near Gravenhurst now open after a fatal collision caused the closure of those lanes.
Bracebridge OPP and emergency crews remain on the scene of a serious crash in the northbound lanes of Highway 11 near Gravenhurst.
Police report a northbound vehicle lost control and rolled into the ditch.
Two of the injured occupants were flown by Ornge air ambulance to a Toronto area trauma centre with serious injuries.
A third person was transported to an area hospital with non-life threatening injuries.
The fourth person died at the scene of the crash.
The OPP says the northbound lanes of Highway 11 at Southwood Road will remain closed for several hours while police trained in collision reconstruction measure, document the scene, and gather evidence.
Bracebridge OPP continues to investigate the cause of the collision.