Officers sighted a suspicious vehicle and a pursuit began near Middlesbrough, the Independent Office for Police Conduct said.
An investigation has been launched into a crash which killed several people following a police pursuit in the early hours of Saturday morning, the police watchdog said.
The Independent Office for Police Conduct (IOPC) is investigating the circumstances leading up to a fatal crash involving a police car and a Volkswagen Passat on the A66 in South Bank, near Middlesbrough.
Officers from Cleveland Police spotted a suspicious vehicle and a pursuit began before the car travelled onto the A66 and collided with a police car at 3.39am, the watchdog said.
An investigation was opened just after 6am on Saturday following a mandatory referral from the force, the watchdog said.
The A66 is closed in both directions between Normanby Road and Church Lane in Eston.
There is significant emergency response at the scene and people should use alternative routes as the road “will remain closed for some time”, Cleveland Police said.
North East Ambulance Service said it had been called to a two-vehicle crash and sent 14 units to the scene including ambulance crews, a specialist paramedic, a hazardous area response team and a doctor from Great North Air Ambulance Service.
