A Markham woman remains in hospital with life threatening injuries after an incident Tuesday night on Highway 401 in the Pickering area.
OPP say a large piece of metal debris was found in the eastbound collector lanes just west of Rougemount Drive around 8:30 p.m.
At least three vehicles had been struck by the debris, which resulted in flat tires and minor damage.
Shortly afterwards, that same debris crashed through the windshield of another vehicle, seriously injuring the 24 year old driver.
The metal is about 2 meters long and appears to be something used to tow vehicles.
Any witnesses are asked to contact the Whitby OPP Detachment 905-668-3388