There is no evidence to suggest the suspicious chemical dumped on the M1 was a "terrorist incident" police have confirmed.
Thames Valley Police, Buckinghamshire Fire and Rescue Service and the EOD continue to investigate the contents of a suspicious black bin-liner found dumped on the M1 under a bridge past Newport Pagnell Services.
Motorisyts on the southbound side have been stranded nine hours between Junction 15 for Northampton and junction 14.
Chief Inspector Mark Lewis of the Joint Roads Policing Unit for Thames Valley and Hampshire said: “We have now reopened the northbound carriageway of the M1.
“Vehicles that have been stationary on the southbound carriageway between the closure at junction 15 and the scene are now being allowed to move past the scene, however the southbound carriageway will remain closed at junction 15.
“There is no evidence to suggest that this is a terrorist-related incident. The object does not contain an improvised explosive device and therefore has been no controlled explosion. However, the object contains a highly corrosive material which has leaked across lanes one and two, therefore the clear up process will take a significant amount of time. Chemical analysis is ongoing to ascertain what the substance within the object is.
“We apologise for the inconvenience caused to motorists but your safety, and the safety of our officers and the staff of our partner agencies, is paramount. We thank the public for their continued cooperation and patience.
“Motorists are advised to avoid the area and the force and Highways Agency continue to divert motorists away from the scene.
“Please continue to check our main Twitter account @ThamesVP, our Facebook page and website for updates.”