Part of the M1 was closed after a body was discovered on the motorway.
The road was closed northbound after on Tuesday between junctions 16 (Northampton) and 18 (Rugby) following the discovery of a man’s body.
Detective sergeant Tony Hopkins, from the collision investigation unit, said: “We can confirm that the body is that of a man and that he appears to have come into contact with several vehicles on the M1. We can only describe the scene and injuries as catastrophic.
“While we have undertaken fingerprint testing, at this stage we cannot confirm the identity of the body until next of kin have been formally notified.
“The focus of our investigation is to establish where this man came from and how he came to be on the M1 and in collision with the vehicles. It may be a fail to stop collision, or it may be that a motorist believed they hit an animal.
“There is no nearby bridge of obvious footpath that would indicate where he may have come from.
“The particular stretch of road is unlit and there are road works restricting the speed limit. People wouldn’t expect there to be a pedestrian in the road.
“It may be an innocent accident or something more serious. The investigation team which includes scenes of crime, disaster collision investigation team, pathologist and other officers, who will now work to determine the circumstances that lead to his death.
“There will be lorry drivers and other motorists who may have driven this stretch of road and some of them may have dash cam footage. We would urge anyone with any information to come forward.
“We will be preparing a report for the coroner.”
The road was opened again on Tuesday afternoon.
The force is appealing for witnesses or anyone with information to call 101 or 03000111222 if outside of the county.