Two separate collisions shut down Highway 3 near Cottam on Wednesday morning.
Both crashes happened around 8 a.m. on Highway 3 between Belle River Road West (County Road 27) and Division Road (County Road 29).
OPP said the first incident involved two vehicles at the intersection of Highway 3 and Division Road. No one was hurt.
The second incident occurred just minutes later on Highway 3 about a half a kilometre west of the initial collision.
Five vehicles were involved. One driver suffered injuries described as serious, and needed to be taken to hospital for treatment. Another driver received minor injuries.
OPP blocked off part of Highway 3 between Cottam and Leamington to allow emergency personnel and technical collision specialists to deal with the scene.
As of 1 p.m. Wednesday, the section of roadway remains closed.