An unmarked police car was not to blame for the death of 15-year-old Scott Turner on the M23, the Independent Police Complaints Commission has concluded.

Scott, from Burgess Hill, was hit by several vehicles after wandering onto the motorway at about 2am on Sunday.

The IPCC carried out its own investigation into the circumstances of the crash because an unmarked police car was involved.

A statement from the IPCC said: "The assessment has found that Scott’s mother called police to report him missing at 1.46am.

"At 1.49am, police received calls from two separate motorists stating that they had hit a pedestrian on the M23.

"At 1.57am, an ambulance, which had been to another accident and was taking people to hospital, reported that they also believed they had collided with a body.

"An unmarked police car, which was following the ambulance, is also believed to have collided with the body.

"The case was referred to the IPCC because of the involvement of the police car."

IPCC Commissioner for the south east Mike Franklin said: “This is a terrible incident and I cannot begin to imagine what Scott’s family is going through at the moment.

"The police are investigating the collision and I would urge anybody who witnessed the incident to contact them so that they can establish exactly what happened and why.

“We have looked specifically at whether the police car involved in the collision could have played any part in Scott’s death. Having examined the various timings involved and looked at the information provided by road collision experts who went to the scene, it appears that Scott had already died by the time the police car became involved.

“If any new information comes to light which suggests that officers could have prevented the collision then it should be re-referred to the IPCC but, based on the evidence available at the moment, I am content to allow Sussex Police to take their investigation forward without further input from us.”

Anyone with information is asked to call Sussex Police on 0845 6070999, quoting Operation Harlington.