Animal rights activists may be responsible for releasing wild boars from a farm in Cumbria, say police.
The boars could easily have reached the motorway, say police
Intruders cut through several fences and pushed over a dry-stone wall at Gatebeck near Kendal, where the boars are kept in woodland.
Cumbria Police said only luck prevented the powerful animals from forcing their way onto the nearby M6.
The incident is being linked to damage at the Highwayman pub in Burrow, Lancashire, where boar is on the menu.
Graffiti was sprayed on the building's walls and cars parked at the pub were damaged.
Two tractors at the Gatebeck farm also had their tyres slashed.
A Cumbria Police spokesman said: "The boars could easily have forced their way onto the motorway and caused a serious collision.
"Whoever did this also put themselves at serious risk when they entered the boar enclosure.
"We are now trying to establish whether it is the work of an animal rights group."