Hampshire Police have now released further details relating to the incident on the M3 Saturday between junctions 10 and 11.
At 3.49am on Saturday 23 September, police were called to the road following reports of potentially hazardous material in the carriageway.
As a result, the motorway was shut for approximately 11 hours between junctions 9 and 11 to allow police, in partnership with specialist hazardous material officers and an Explosive Ordnance Disposal Team, to assess the substance.
Early assessments indicate that this was a flammable material, not explosive material, which had been thrown from the motorway bridge which leads to St Catherine’s Hill. Nobody was hurt, and there is no wider risk to public safety as a result.
Assessments to determine exactly what the material is are still on-going at this time.
Police have been utilising a wealth of expertise, across policing and our partners, to assess the risk to public safety, and we stress that at this time this is not being treated as a terrorist incident.
Officers are aware of, and are investigating, a similar incident which took place on the same bridge last week, at around 4am on Saturday 16 September.
In this incident, an object was dropped into the carriageway and we received further reports that something was alight in the same location.
Officers attended and found a quantity of broken glass but no fire. A lane 1 closure was put in place for a very short time, to allow the debris to be cleared. No-one was hurt during this incident.
Police know that a lot of people use this route at that time as part of their daily routine, and urge anyone who witnessed either of these incidents, or who has any information, to contact police immediately on 101.
Did you see anyone on the bridge? Did you see anyone acting suspiciously in the area?
A Police spokesperson said:
'We thank you for your patience and co-operation as we investigated yesterday’s incident, but again would like to reassure you that this is not being treated as a terrorist incident.'