Explosive officers are investigating after a number of unidentified items were found in woodland near the M40 in Buckinghamshire.
Police were called to the motorway between junctions three and four, near High Wycombe, after the items were found by the public on Wednesday night.
The material found has now been removed from the scene, police said.
The Metropolitan Police said explosives officers were called to the area, but forensic experts remained at the scene.
A Metropolitan Police spokeswoman said explosives officers had been called to the area in Buckinghamshire on Wednesday as a precaution.
The spokeswoman said she could not comment on whether the search was related to an earlier search of woods in High Wycombe in connection with an alleged airline bomb plot.
One lane of the eastbound M40 was closed, but has now reopened.
The hard shoulder remained closed, the force said.