SALEM — Mink that tested positive for COVID-19 at an Oregon farm in November appear to have recovered, according to state agriculture officials.

Animal advocates, however, remain concerned after one mink caught just outside the farm tested positive for low levels of the virus, potentially exposing other wildlife to infection.

Dr. Ryan Scholz, state veterinarian for the Oregon Department of Agriculture, visited the farm Nov. 23 and collected 10 mink samples that were sent to Oregon State University and USDA for testing. All samples came back positive for the virus.

It is believed the mink contracted COVID-19 from workers at the farm, which was placed under quarantine. ODA has not identified the operation or disclosed its location.

Oregon has 11 permitted mink farms with an estimated 438,327 animals, making it the fourth-largest pelt-producing state after Wisconsin, Utah and Idaho. Eight of Oregon’s mink farms are in Marion County, two are in Clatsop County and one is in Linn County.

Since the initial positive tests, ODA has conducted two rounds of follow-up testing documenting the animals’ recovery. The first round was conducted Dec. 7. Of 62 mink sampled, only one showed “barely detectable” levels of the virus.

The second round, conducted Dec. 21, resulted in no positive tests. ODA says it will conduct one more round of testing before deciding whether to lift the quarantine.

“We’re doing a lot of work to ensure that this virus did not — and does not — escape this farm,” Scholz said. “That work will be ongoing until we can ensure this is not a risk.”

Generally speaking, Scholz said mink farms in Oregon process animals on-site and send raw pelts to processors out-of-state. The carcasses may be sold as crab bait, given to zoos or used to make organic compost, according to Fur Commission USA.

“In this case, they will be disposed as potentially infective,” Scholz said. “They’ll go likely to the landfill and be buried.

Pelts and carcasses at the farm will remain under quarantine until ODA, USDA and the Centers for Disease Control and Prevention come up with a disposal plan, he said.

“We haven’t gotten there yet,” Scholz said.

Meanwhile, USDA Wildlife Services, under the direction of the Oregon Department of Fish and Wildlife, continues to trap and test local wildlife to ensure the virus does not spread. One mink believed to have escaped from the farm was caught Dec. 13 and tested positive for low levels of COVID-19. Scholz said it was discovered just a few dozen yards from the compound, and matched the size and color of other minks at the farm.

It was also showing signs of acute, short-term starvation, an indication it had recently escaped. Biologists have tested eight other animals, five opossums and three cats, which all were negative for the virus.

“There is no evidence that (COVID-19) is circulating or has been established in the wild,” Scholz said. “Still, we are taking this situation very seriously and continuing to survey and trap near the farm.

“Also, we have asked USDA to run additional tests on the trapped mink, including sequencing the viral genome and a DNA test to ensure we know exactly where this mink came from,” he said.

Previous outbreaks of COVID-19 in farmed mink have been reported in Utah, Michigan and Wisconsin, as well as six countries around the world, he said.

The situation in Denmark was particularly severe, where health officials discovered a mutated strain of the virus that threatened to undercut the effectiveness of a vaccine.

In response, Denmark culled its entire population of farmed mink — more than 17 million animals. To make matters worse, the Wall Street Journal reported, the Danish parliament voted to exhume 5.5 million of the dead mink from mass graves beginning in May after environmental inspectors found that some water sources might have been contaminated by bacteria as the mink decay.

Fearing a similar threat in Oregon, the Center for Biological Diversity, an environmental group, has urged ODA, the Oregon Health Authority and Gov. Kate Brown to release more information about the November outbreak. Lori Ann Burd, environmental health director for the group, said it was “beyond outrageous” that an infected mink was able to escape quarantine at the farm, and “putting an untold range of wild animals at risk of contracting the virus.”

As much as I hope this case of COVID-19 is just limited to the one mink they tested in the wild, we know this virus is highly contagious and that one case quickly grows to many,” Burd said in a statement. “It breaks my heart to think about how COVID-19 could tear through wild animal populations.”