Seven people including two police officers were killed in the crash on the A66 in the early hours of Saturday
Police aborted the pursuit of a car seconds before it crashed while going the wrong way down a dual carriageway, killing all five men aboard and two officers, investigators have said.
Michael Robert Cahill, 23, Jacob Matusiak, 23, Theo Rae, 17, Makai Saddington, 18, and Cole Robert Worthy, 17, died when a Volkswagen Passat struck a Cleveland Police vehicle on the A66 near Middlesbrough on Saturday.
PC Matthew Blades, 37, and PC Tom Clough, 38, who were on the correct side of the road and were helping search for the car, were also killed.
The Independent Office for Police Conduct (IOPC) said the force had been pursuing the Passat following reports of "numerous incidents" linked to it.
PCs killed in A66 crash were heroes, say families
The watchdog, which launched an immediate investigation into the crash, said the Passat was believed to be using cloned registration plates which activated an ANPR (automatic number plate recognition) camera.
Analysis of footage from one of the police vehicles showed the pursuit lasted just under seven minutes before the Passat travelled on to the wrong side of the A66, at which point officers "aborted" it, the IOPC said.
The pursuing officers continued to travel on the correct side of the carriageway but approximately 10 seconds later, at about 03:39 BST, the Passat collided with the marked armed response vehicle which was "in the area to assist in a search" for the car, a spokesman said.
Security footage from a house on Lime Road in Middlesbrough appears to show a car being pursued by police vehicles three minutes before the crash.
Watch: Video appears to show police pursuit minutes before fatal crash
When someone dies following police contact, it is mandatory for the case to be referred to the IOPC.
Its director of engagement, Derrick Campbell, said the watchdog recognised the "devastating impact" the crash had on Cleveland Police and the "wider policing community".
He said: "We have obtained initial accounts of officers involved in the pursuit, the incident log and in-car footage of the incident.
"Work is ongoing to obtain additional material.