The M4 is closed in both directions after a body was found on the carriageway between junctions 20 (Almondsbury Interchange) and 21 (Awkley).
Police were called at 6.40pm on Saturday 22 February by several drivers reporting something in the road.
Officers attended and found human remains.
Enquiries are underway to identify the deceased and notify next of kin, while an investigation to establish how the person came to be on the motorway continues.
The road is expected to remain closed into the early hours of Sunday 23 February.
Police are keen to hear from anyone who was travelling along that stretch of the M4 has any relevant information or dashcam footage. If you can help please call 101 and give the reference 5224047292.
Please follow National Highways: South-West on X for updates: https://orlo.uk/7GdPJ
