Two people were killed in a devastating crash north of Hamilton on Thursday morning as Waterloo Regional Police pursued a auto.
How Waterloo police were involved was not immediately clear.
When the driver did not stop, Haffner says a pursuit was initiated that ended with the fatal collision.
SIU spokesperson Monica Hudon said its investigators understand that Waterloo police were responding to a possible assault when officers attempted to stop a vehicle on King Street East in Cambridge.
About 20 minutes later, the vehicle slammed into an oncoming transport truck on Highway 6 near Campbellville Road.
Both occupants of the vehicle were pronounced dead at the scene.
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The Special Investigations Unit (SIU) has now taken over the investigation and Waterloo police said it will no longer be commenting. The truck driver was not hurt.
"That would be a part of our investigation". But the unidentified man and woman in the vehicle were killed instantly. "It's still very early on", she said.
OPP Sgt. Kerry Schmidt is on scene and is expected to issue an update to reporters shortly.
The SIU is an arms-length agency that investigates incidents involving police in which someone is killed, injured or accused of sexual assault.
Hudon also would not say whether police were in fact pursuing the auto when it collided with the truck.
Police expect the area to be closed for most of the day.