Six monkeys died of unknown causes while in quarantine at the Oregon Zoo last Saturday. The six cotton-top tamarins were found dead by veterinary staff.
Zoo officials say the monkeys belonged to a group of nine tamarins that arrived at the zoo on May 22. They say the remaining three monkeys appear to be in good health. Those monkeys are being closely monitored.
Tim Storms, veterinarian with the Oregon Zoo, says the zoo is investigating the cause of the monkey deaths.
"We're working to try and find out why," Storms says. "They've got post-mortem exams and we're waiting for histopathology results to come back shed some light on that."
Zoo officials hope to receive the results within a few weeks.
In January, a twenty-year-old male orangutan died at the zoo after a sudden illness. Earlier this month, the former zoo director and senior veterinarian were fired. Metro concluded that "mistakes were made" in the case of the Orangutan's death.
This story originally appeared on Oregon Public Broadcasting.