The concourse has since reopened.
At 8:40 a.m. on Tuesday, a small electrical explosion went off in a maintenance shed near Gate D21. Airport officials evacuated passengers waiting at Concourse D to Concourse E during a power outage caused by the explosion.
Power was restored by 11 a.m. There were no reported injuries. There was no fire or smoke reported, and the explosion only caused minor damage to the shed.
Passengers that returned to the concourse said the situation there is normal, despite a minor power outage still in effect.
The cause of the explosion is under investigation by Atlanta police. FBI Special Agent Stephen Emmett said the event did not appear to be terrorist-related, and the bureau will not be involved with the investigation.
Hartsfield-Jackson is the country's busiest airport and the home hub of Delta Airlines.