Ontario Provincial Police say Highway 7 in Whitby is closed in both directions just east of Highway 412 after a multi-vehicle crash on Wednesday morning.
The crash happened at around 10:07 a.m. prompting the highway to close between Coronation Road and Cochrane Street.
OPP Sgt. Kerry Schmidt said the crash involved four vehicles with three of them travelling westbound and one eastbound when a head-on collision occurred.
Schmidt said four people were taken to hospital. Two of them were airlifted in non-life threatening condition.
Ornge air ambulance attended the crash and said they transported a man in his 60s with critical injuries to a Toronto trauma centre.
The other two people were taken to a local hospital with relatively minor injuries, Schmidt said.
There is no word on when the road will reopen but its expected to remain closed for hours.