Ontario's Special Investigations Unit has identified the victims of Thursday's fatal collision on Highway 6 between Guelph and Hamilton, Ont. as 15-year-old Nathan Wehrle of  Cambridge and 16-year-old Taryn Hewitt of London.

The passenger in the vehicle is thought to have been Wehrle's girlfriend.

Friends of both youths have shared condolence and remembrance messages on family Facebook pages. 

Another youth, who spoke to CBC News, said he and the dead driver had previously been involved in car theft and joyriding. He said he received a message from Wehrle on Monday, alleging that "he and his girlfriend stole the car together."

The transport truck driver involved in the head-on collision was shaken but uninjured. 

Police chase

Waterloo Regional Police began to pursue a red car after what they describe as "a concerned citizen" called police saying they witnessed a woman being assaulted and pulled into a car in Cambridge.

Police attempted to pull the car over on King Street East in Cambridge, but the male driver fled and led police on a chase down Highway 401 toward Toronto, and then turned south on Highway 6 toward Hamilton.

The car crashed head-on with a transport truck at a curve in the road between Freelton Road and Concession 10, north of Hamilton just before 10 a.m. Thursday morning.

It's believed that the vehicle involved in the crash may have been a red Pontiac G6, but the collision was so violent and the damage so extreme that some initial responders at the scene could not immediately identify the make and model.

OPP, SIU take over 

On Friday, the Ontario Provincial Police took over the investigation into the Cambridge incident. SIU is investigating the crash, because of potential police involvement. The SIU investigates when someone is seriously injured or killed during an interaction with police in Ontario. 

"We felt it was prudent as an organization to reach out to the Ontario Provincial Police as the Special Investigations Unit is conducting the collision investigation," Waterloo Region police Insp. Michael Haffner told CBC News Friday.

"We have the utmost confidence in our own members to conduct the investigation, but felt that — due to the circumstances — from an accountability and a transparency perspective an outside agency would better suited."