Police have confirmed the suspicious item found on the M1 in Northamptonshire is not explosive - but it could contain some form of chemical.
Motorists have been stranded between junction 15 and 14 of the M1 for close to nine hours now after the object was reported to police at around 7.30am.
One witness described the item as a black bin liner with "steam/vapour of some kind rising from it".
Youtube footage taken from a drone shows a bomb disposal robot dragging a black rubbish bag, which appeared to have contained a yellow substance.
Thames Valley Police has now confirmed the suspicious object is not a crude bomb.
A Thames Valley spokesman said: "Continues to work alongside Buckinghamshire Fire and Rescue Service and the EOD, following the discovery of a suspicious object on the M1 under a bridge past Newport Pagnell Services on the carriageway between Junction 15 and 14.
"Investigations by the EOD can confirm that there is no explosive element to the object found, however, chemical analysis is ongoing on the object to ascertain what the object might be but it appears to be some form of chemical.
"At this time the M1 remains closed in both directions, Thames Valley Police and the Highways Agency continue to divert motorists away from the scene, and we are continuing to move people who have been stuck on the carriageway away from the scene.
"Thames Valley Police officers and the Highways Agency where possible are providing assistance to anyone who requires it as a result of being stuck in the tailback.
"We would continue to advise motorists to avoid the area."