Atlanta police Officer DT Hannah said the package was "cleared" and the terminal was reopened this morning.
Airport officials said bomb-sniffing dogs had indicated "a positive hit" while checking an unattended bag in the South domestic terminal around 9:41 AM local time today. They said passengers were allowed to re-enter the terminal less than 30 minutes later.
The evacuation comes one day after attacks at an airport and subway system in Brussels, Belgium, killed at least 34 people, including three suicide bombers, and injured 270 others.
