Special Branch are investigating the release of about 140 wild boar from a farm in Devon.
Police and neighbours are helping the farmer trace the remaining boar
Half the herd have been rounded up after vandals cut through an enclosure and released animals from the farm in Holsworthy for the second time.
The damaged perimeter fence was found at Bramblewood Farm in Rydon Lane at about 0800 GMT.
Boar farmer John Walker said: "Special Branch were called in last time and are looking at what happened today."
Police and neighbours are helping trace the remaining boar.
Mr Walker lost about 60 boar after fencing and padlocks were damaged in November 2006.
Mr Walker who owns and runs the boar farm said: "The fencing contractor has just finished repairing the fences.
"They're all in the wrong pens, so we're going to have to sort them out and then feed them."
He said they expect more boar to be rounded up overnight because hunger would force them closer to their enclosures.
But he added that some animals may die because they are unable to forage in the wild for themselves.
Police are appealing to members of the public to keep away from the animals if spotted and have warned they may charge without any provocation.
Anyone who sees the boar is asked to call police immediately.
Police said they were keeping "an open mind" about the motive for the vandalism.
Other herds of wild boar are believed to be roaming free after a number of attacks by animal rights activists to fencing at Allan Dedames' Woodland Wild Boar Farm near South Molton, about 20 miles away from Holsworthy.
Activists released 102 boar from the farm in December 2005 and another 45 were set loose in a second attack in February 2006.
Mr Dedames lost his appeal in September against North Devon District Council's decision not to reissue him with a Dangerous Wild Animals Licence.