Four people were taken to hospital after a crash on Hwy. 410 and Courtney Park early Saturday morning.
Paramedics say two people suffered critical injuries and were taken to a trauma centre, while two others suffered minor injuries.
The northbound 410 ramp to Courtney Park Drive was closed for several hours while crews removed the vehicle and police investigated.
It's not clear what caused the collision.
OPP say the male driver in the single-vehicle crash suffered minor injuries and was taken into custody.
Police did not say what charges he is facing.