A serious crash on the 401 in Mississauga has all eastbound lanes closed at Winston Churchill.

The OPP says road crews were cleaning up an earlier crash when a tractor trailer slammed into the back of an MTO truck causing a chain reaction.

The result was one of the workers standing on the shoulder was struck by a pickup truck and sent to Sunnybrook in critical condition.

His injuries were then downgraded to serious but non life threatening. The driver of the trailer is also in hospital with serious but non life threatening injuries.

OPP Sgt. Dave Woodford the says the highway was expected to reopen at 6 this morning but it was closed for the entire morning rush.

Crews now have to resurface the road and the hope is that it will be completed by the afternoon rush.