A driver who left his car during a police pursuit died when he was hit by the patrol vehicle in County Durham.
Kelvin Bainbridge's Nissan Primera was followed after failing to stop in Spennymoor, on 18 October.
The 19-year-old got out of the moving car, which then crashed, in Central Drive, and he was hit by the marked police vehicle.
Durham Police referred the matter to the Independent Office for Police Conduct (IOPC).
The watchdog said the investigation was in its early stages, but footage of the incident and initial accounts from some of those involved had confirmed the pursuit had lasted about six minutes in total.
'Tragic and upsetting'
In addition, Mr Bainbridge, who had failed to stop when indicated, had got out of the Nissan while it was still in motion.
David Ford, from the IOPC, said: "Although our work is still in its early stages we have made good progress so far.
"We are aware that rumours have been circulating on social media surrounding the details of the incident.
"We appreciate that this was a tragic and upsetting incident, but it is important that people do not engage in unhelpful rumours and allow us to carry out a thorough and impartial investigation."