The northbound and southbound Bayview-Bloor ramps have reopened on the Don Valley Parkway following a multi-vehicle crash early Thursday morning.
Toronto police said three vehicles were involved in the collision causing a rollover.
Paramedics said three people were taken to hospital.
Two suffered minor injuries and a third was rushed to a trauma centre with serious injuries.
Police said one person was arrested at the scene for impaired driving.
Motorists were told to avoid the area. The ramps were reopened just around 10 a.m.