The attack is the second such incident for Bramblewood Farm in Holsworthy, and while 70 boar have been rounded up, as many again are still on the loose.
Police and neighbours are helping to trace the remaining boar. Farmer John Walker lost 54 boar after fencing and padlocks were damaged in November 2006.
Police are appealing to members of the public to keep away from the animals if spotted and warn 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 damage.