The zoo said male bongo Tambo "briefly left his habitat" Wednesday and zoo visitors were taken to the nearest buildings as a safety precaution during the incident, WSB-TV, Atlanta, reported Thursday.
Officials said Tambo appeared calm during the incident and did not show any signs of aggression toward the on-site veterinarians who were able to tranquilize him and return him to his holding area.
The officials said they are investigating the escape.
Eastern bongos, native to eastern Africa, are considered critically endangered.
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