Mounties in Surrey say they're treating a fiery crash near the Peace Arch border crossing that left a man dead Thursday as a criminal matter.

In a statement, police said the two-vehicle collision took place at around 11:30 a.m. on Highway 99 some 300 metres north of the border.

"Investigators determined a Porsche Cayenne SUV collided into a Toyota Sienna van causing the van to catch fire," investigators said.

The driver and sole occupant of the Toyota was pronounced dead that the scene. The deceased's identity has not been released, but the BC Coroners Service confirmed Friday he was a man.

The Washington state man driving the Porsche suffered non-life-threatening injuries only and was taken into custody, but later released, police said. He was also alone in his vehicle.

Witnesses told CTV News Vancouver that man was taken into custody after stumbling out of the SUV.

Mounties said they're treating the crash as a criminal investigation unless they determine otherwise.

"Until there are factors that would suggest this is not a criminal investigation, we are treating it with the utmost seriousness," said Cpl. Elenore Sturko.

The investigation is proving incredibly complex, with a significant fire that burned abnormally hot following a fierce thud.

"I heard the loud boom and felt it underneath," witness Kohn Kageorge told CTV. "The ground shook and I was inside the house at the time."

That intensity has fuelled speculation that the minivan might have been carrying gas cans full of cheaper fuel bought in the U.S., but investigators have not been able to confirm that detail.

"We're still at this time working with the BC Coroners Service to determine and confirm the identity of the individual who was killed as a result of this serious collision," Sturko said.

The collision shut down Highway 99 in both directions for several hours.

Southbound lanes and the border into the U.S. reopened within hours, but the northbound side remained closed until Friday morning.

Even though they're no longer at the scene, investigators said they're still in the evidence-gathering phase and won't reveal what they think caused the deadly collision.

With files from CTV Vancouver's Penny Daflos