KNOXVILLE, Tenn. (CBS/AP) — Thirty-three reptiles were found dead last week at the Knoxville zoo, and officials there say they have no clues yet about how it happened.

Zoo Knoxville told local news outlets that nearly all of the dead animals were snakes. They were all found dead in the reptile area. Surviving animals were removed and given oxygen.

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Zoo officials have stopped using the reptile area for animals while the deaths are investigated.

“We don’t know exactly what occurred to cause this terrible event, but we do know it was isolated to a single building. We are continuing to investigate all the physical systems and conducting necropsies to see if we can gain any insight,” the zoo said on its Facebook page.

Zoo Knoxville President and CEO Lisa New calls the deaths a “devastating and catastrophic loss.”

“These animals were important ambassadors who helped so many people understand the role snakes and lizards play in the balance of nature. We also lost breeding programs for several endangered and threatened species. It is especially difficult for our herpetologists who have dedicated their careers to caring for and advocating for these animals,” New told CBS Knoxville affiliate WVLT-TV.

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Director of animal collections Phil Colclough says tests being conducted include checking for harmful gases in the building and for mechanical errors on thermostats.

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