The Animal Liberation Front has reportedly claimed responsibility for smashing cages and cutting wire at the farm near Ringwood, Hampshire.
Up to 6,000 mink escaped into the New Forest, a National Park and home to some of Britain's rarest birds. Animal welfare groups including the RSPCA condemned the action, as the farm-reared animals would be unable to survive in the wild and die of starvation.
Several hundred are already believed to have been shot by gamekeepers or run over, though around 500 were returned to the farm over the weekend.
The surviving animals, which can be up to 28in long, could endanger rare birds and fish nurtured in the park, as they will eat almost anything - from eggs to small mammals. Conservationists compared the effect of releasing the predators - which are not native to Britain - to pouring a tanker full of chemicals into a stream.
Forest-keeper Howard Taylor had previously raised concerns about the hazard of a mink farm so close to the environmentally sensitive National Park.
He said: "Whoever let these animals out, if they think of themselves as environmental warriors they should have thought of the environmental consequences of releasing such a vicious predator into such a delicate ecosystem.
"The New Forest is one of the jewels in Britain's environmental crown. Heathland is a disappearing habitat on an international scale and releasing these numbers of mink into it is like putting a tankerful of poison in a river. They can climb a tree like a squirrel and dive in a stream like an otter. They are an efficient killing machine and our native species are not used to having to cope with them."
He said he expected to be dealing with the consequences for years to come.
District councillor Ann Drake said that mink had been swarming over local properties and had already been seen in Ringwood town centre and the nearby River Avon, around three miles away.
She said: "It is an ecological disaster. Everyone in the area is devastated. Anyone with a shotgun has been out hunting them, and I understand that seven or eight hundred have been shot."Reuse content