Hundreds of mink have already been found dead Nicholas Kraemer

Efforts are underway to recapture thousands of mink that were released from a Stearns County farm, but many have already died.

Vandals broke into Lang Farms near Eden Valley Sunday night and released up to 40,000 animals, which were being raised for their pelts.

Stearns County Chief Deputy John Lentz said about 90 percent of the recaptured mink died soon after being caught and returned to their cages. As of Tuesday morning, they'd buried about 5,500 animals, Lentz said.

"At this point, they suspect stress," he said.

Lentz said the sheriff's office doesn't have any leads or suspects in the case yet. The FBI is assisting in the investigation.

Stearns County Sheriff Don Gudmundson said Tuesday he believes members of an animal rights group released the mink, but didn't steal any of the animals.

"It's pretty hard to steal 30,000 to 40,000 mink. What are you going to do put them in a trunk? They'd chew your fingers off," Gudmundson said.

Lentz said the mink are housed in about 25 to 30 separate buildings, so it's likely multiple people were involved in the release.

"It's not something that could have been done by one or two people acting randomly," he said. "This was something that they went there intentionally to do, and it would have taken more than a couple of people to accomplish that."

The loss of the mink is estimated at $750,000. That amount could go as high as $1 million, Lentz said.

It's unlikely that the captive mink can survive long in the wild, said Fred Bengtson, wildlife manager for the Minnesota Department of Natural Resources.

"They're really kind of a different animal than wild mink in that they don't necessarily have the instincts to forage on their own," Bengtson said. "So it's really kind of a tragic thing."

The mink farm is near a wildlife management area and waterfowl production area. But Bengtson said he isn't too concerned about the mink causing long-term harm to native wildlife.

"These animals are so conditioned and so tame, so to speak, that their ability to survive probably much longer than a week is really, really limited," he said.

A neighboring farmer found 10 of his chickens dead, Lentz said. He suspects the mink were responsible.

The sheriff's office is asking anyone with information to call 320-251-4240. The Tri-County Crime Stoppers is offering a $1,000 reward for information leading to an arrest and conviction.

The Associated Press contributed to this report.