HELENA, Mont. (AP) — A Montana game farm is under quarantine after an elk tested positive for chronic wasting disease, the state Department of Livestock reported.

The brain wasting disease hasn’t been identified in domestic deer or elk in the state since 1999, officials said.

The elk appeared healthy and was slaughtered for meat, but the illness was discovered in testing required by the U.S. Department of Agriculture’s Herd Certification Program. State officials did not identify the game farm involved or say where it was located, citing confidentiality requirements.

The Livestock Department placed the herd under quarantine while the cause of the infection is investigated.

Montana law requires CWD-positive game farm herds to be quarantined for five years or for all the animals to be killed and tested for the disease.