One or more intruders broke into an Iowa mink farm and released 2,000 of the furbearing animals in what a trade group called a "terrorist act" under federal law.

Sometime between Monday night and Tuesday morning, fencing was cut and pens and nest boxes were destroyed to release the mink, which are raised for their pelts, Fur Commission USA said. The farm is near Woodbine, Iowa, about 100 miles (161 kilometers) west of Des Moines.

Just over 60% of the mink had been recovered by Friday morning, though time is running out to find them all before they succumb to threats in the wild, Fur Commission USA Executive Director Challis Hobbs said.

People have attacked mink farms similarly and been charged under the federal Animal Enterprise Terrorism Act, which defines a person as a terrorist if they are trying to impede or ruin an animal operation, Hobbs said.

About 275 mink farms in 23 states operate in the U.S., producing about 3 million pelts a year worth more than $300 million, according to Fur Commission USA.

One to two mink releases occur on farms in the U.S. each year, Hobbs said. The motive is presumably compassion, he said.

"What we see time and time again is when they release captive-raised, farmed mink into the wild like this, especially in these kinds of numbers, it does the exact opposite by hurting and harming the animals," he said.

If mink can't be recovered within 24 to 48 hours, the majority die without access to food, clean water and shelter, he said. Farms are required to follow humane treatment and euthanasia standards for the animals, Hobbs said.

Some of the released mink attacked and killed some of the ducks and geese the farmer was raising for repopulation efforts, Hobbs said.

The farmer, his son and grandson were still collecting mink, with more than a dozen live traps deployed and checked routinely, Hobbs said.

Harrison County Sheriff's Office Sgt. Todd Denton declined to comment on the investigation. Through Hobbs, the farmer declined an interview.

Advocates with the Animal Legal Defense Fund did not immediately respond to a request for comment.

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Dura reported from Bismarck, North Dakota.