Lab results have revealed that the deaths of 34 reptiles at Zoo Knoxville back in March were most likely due to a toxic agent, but unanswered questions remain. The animals were found dead in their cages by zoo keepers on March 22. All of the reptiles died in the zoo’s reptile complex. After the animal’s death, the decision was made to take the building out of use. The zoo said they are still not sure how the reptiles were poisoned. The blood of affected and unaffected animals was tested for multiple toxins and none were found, but veterinarians at the University of Tennessee College of Veterinary Medicine determined swollen blood vessels and changes in the liver and heart of the animals were consistent with a toxic agent. Iconic snakes popular with visitors, including a forest cobra and albino Eastern diamondback rattlesnake and three critically endangered species, the Louisiana pine snake, Catalina Island rattlesnake and Aruba Island rattlesnake, were among the fatalities.