The 401 westbound and eastbound near the Quebec border has reopened after a plane crashed along the highway.
The OPP put out the notice on social media just after midnight.
The plane involved is a Cessna 150, a two-seater aircraft commonly used for flight training and personal use.
The occupants were transported to the hospital in critical condition.
The joint rescue co-ordination centre and transport safety board are assisting with the investigation.