Police closed off a Northampton service station while they surounded a lorry during an incident today.
Northampton Services on the M1 northbound and the entry road to the A43 were closed at around noon by police, though it is still unclear what the police incident was.
A spokeswoman for Northamptonshire Police said the force was assisting the Metropolitan Police in an operation, though The Met is yet to confirm the details.
Eyewitnesses have reported seeing people running towards the motorway carriageway while being pursued by police and a dog unit.
Video footage taken by a driver stuck on the entry slip road appears to show a number of officers surrounding a lorry.
More details to follow.