An early evening crash east of Stratford, Ont., sent six people to hospital on Thursday.
Perth County OPP said the collision happened around 5:30 p.m. OPP officers responded to the scene along with members of the Perth East Fire Department and Perth County Paramedic Service.
Police said officers were investigating the crash, which took place on Highway 8.
Investigators said the crash involved five vehicles and that they were told a transport truck collided with three cars and a minivan.
A total of six people were treated by paramedics and transported to hospital. One person was later transferred to London for further care.
On Friday morning, Perth OPP said one of the victims remained in critical condition in hospital, and the cause of the collision remains under investigation.