The coroner has confirmed the cause of death in the crash that killed five Prince George people on Thursday.

"In terms of confirming all identities and any testing we needed to do on the victims, that is completed and it is as expected. They clearly died of injuries suffered in the crash," said Barbara McLintock of the BC Coroners' Service.

It was already commonly known, but not officially confirmed, that the deceased in the collision were Matt and Leah Altizer, their children Jonathan and Emily, and Matt's sister Heather Kress. All were travelling south in an SUV that crossed the centre line into the path of an oncoming tractor-trailer unit in between the Cariboo communities of McLeese Lake and Macalister just north of Williams Lake.

Due to the violent impact and then an intense fire that kept emergency responders at bay for a prolonged period of time, the post-mortem examinations were helpful in establishing one fact above all, particularly for their loved ones.

"It is absolutely true that the deaths were virtually instantaneous," McLintock said. "A fire department could have been sitting across the street, and it would have made no difference. All died in very sudden fashion."

The cause of the crash is still under heavy police investigation, she said. It will be a long process to officially confirm what it was that took Altizer's vehicle over the centre line that day.