A man and a woman are dead following a police chase on a highway south of Guelph, Ont.

The crash between a red car and a transport truck happened just before 10 a.m. Thursday on Highway 6. Waterloo Regional Police officers had been pursing the car after a concerned citizen called police after witnessing a woman being assaulted and pulled into a car.

That car was found on King Street East in Cambridge.

"We located the vehicle believed to be involved and when we attempted to pull that vehicle over to speak with the occupants and check on the well-being and safety of the female, the driver chose not to stop [at] which point the pursuit was initiated," Insp. Michael Haffner told CBC News.

That happened at 9:30 a.m. The suspect vehicle then drove east on Highway 401, then turned south onto Highway 6. At 9:55 a.m. and about 30 km away from the spot where officers tried to stop the car, the car collided head-on with a transport truck.

Female in car may have been abducted

The male driver and the female passenger of the pursued vehicle were pronounced dead at the scene of the crash. Haffner said it is believed the female in the vehicle may have been the same female seen being pulled into the car in Cambridge, but the investigation is ongoing.

"It is possible that the individuals that this concerned citizen called about were the ones in the vehicle when the collision occurred," Haffner said.

Crash in Freelton

A Google maps screenshot shows where the collision occurred and that the road is now closed. (Google)

"I have notified our investigative branch to look into the circumstances leading up to and why our officers initially responded to the address in Cambridge for what was believed to be a possible abduction and assault of the female," he added. "That will continue until we're satisfied we can identify the circumstances in relation to that."

The transport truck driver was shaken but uninjured. 

Regional police officers involved were also not injured and returned to Cambridge where they were expected to speak to Ontario's Special Investigations Unit, which has invoked its mandate to investigate the collision. The SIU investigates when someone is seriously injured or killed during an interaction with police in Ontario. 

Haffner said the officers were being monitored for any health needs.

The crashed vehicle was completely destroyed, with damage and debris so extensive that first responders at the scene had difficulty identifying the make and model. 

Police investigate crash highway 6 waterloo regional police

Investigators place markers at the scene of a fatal head-on crash between a red vehicle and a transport truck Thursday morning on Highway 6 north of Hamilton. Two people in the red vehicle were pronounced dead at the scene. The driver of the transport truck was uninjured. (Kate Bueckert/CBC)

'Devastating' collision

SIU spokesperson Monica Hudon said they cannot confirm whether police were still pursuing the suspect vehicle at the time of the crash.

"The investigation is in the very early stages," Hudon said at the scene. "It's quite a tragic collision."

She also was unable to say how many Waterloo Regional Police officers were involved. At least three cruisers were at the scene.

OPP Sgt. Kerry Schmidt called the crash "horrific."

"This is an absolutely devastating collision. Massive amounts of damage, trauma and debris all across the highway," Schmidt said.

"This is an absolutely devastating collision. Massive amounts of damage, trauma and debris all across the highway."  OPP Sgt. Kerry Schmidt

Hamilton fire spokesman Claudio Mostacci said firefighters responded to reports of a transport truck colliding head-on with a vehicle.

Mostacci couldn't say the cause of the collision or the status of any patients transported by paramedics. There was a fire in the transport truck but firefighters extinguished it quickly, Mostacci said.

​Highway 6 is an important link between the cities of Guelph and Hamilton. The crash, between Freelton Road and Concession 10 southeast of Puslinch, Ont., has closed the highway in both directions. It is not expected to reopen until Thursday evening.

Hudon said investigators were working Thursday afternoon to identify the individuals killed in the crash.