Police responded to reports of a male cyclist being hit by a vehicle in the Dixie and Rathburn area around 5:45 p.m.
Police say the man was taken to a trauma center with potentially life-threatening injuries.
According to the police, the driver did not stay at the spot but he and his vehicle were located a little while later and he is now in custody.
There are closed roads in the area for exploration.
Police ask anyone who may have seen the incident to contact them at 905-453-3311.