The M5 is closed in both directions after a body was found on the carriageway.
Officers have closed the motorway between junctions 11A at Brockworth and junction 12 for Quedgeley.
The incident was reported shortly before 4.10am this morning.
Officers attended the scene, on the southbound carriageway around a mile north of Gloucester Services, and have closed both sides of the motorway while the body is recovered and a serious investigation takes place.
Police have also reportedly sealed off The Ash Path bridge that runs over the motorway.
Diversions have been put in place, with the closure likely to remain in place for a number of hours while officers establish the circumstances of the incident.
Diversion: southbound to follow solid black circle, northbound to follow the solid black triangle route via A417, A38 and the B4008 through Gloucester.
Gloucestershire Constabulary is now appealing for dashcam footage and witnesses.
Investigating officers are keen to hear from anyone who travelled on either the northbound or southbound carriageways between junctions 11 and 12 between 3.45am and 4.20am.
Anyone who has dashcam footage and travelled in the area at this time is asked to call police on 101 and reference incident 34 of October 30.
Information can also be submitted to police online via http://bit.ly/36kUWxt.