A woman has been airlifted to hospital with critical injuries, her son also hurt after a rollover on Hwy 403.
It happened in the highway's eastbound lanes near Erin Mills Pkwy at about 1:30 p.m. Sunday.
Police haven't been able to so why the vehicle with the 29-year-old woman at the wheel and her six-year-old son inside rolled.
Passersby rushed to help stabilize the mangled vehicle which seemed to be balancing on a steel guardrail. The vehicle's roof needed to be cut off to get the woman out.
The woman's injuries are described as critical but she is expected to survive. Her son suffered minor injuries and was taken to hospital as a precaution.