A spokesperson for US Airways said that a transformer that overheated caused the explosion in a construction area near Concourse D on Tuesday.
The explosion happened in a maintenance shed around 8:40 a.m.
Airport officials said the a small electrical explosion near Gate D 21 at a ramp level maintenance shop.
Passengers on the north side of Concourse D were evacuated to Concourse E.
There were no reported injuries, and there was no fire.
Delta and AirTran are reporting minimal delays as a result of the small explosion. A US Airways representative said the airline canceled two small flights and rerouted one headed to Atlanta.
Chris Dittoe, Indianapolis, said he had landed in Atlanta as concourse D closed.
"It was frustrating because we sat on the plane for an hour and we had no idea why," said Dittoe.
Matthew Lembo, Atlanta, said he received a text notifying him that his noon flight to New York had been delayed 35 minutes.
Passengers said the explosion wasn't a huge inconvenience.
Power was restored and all operations resumed just before 11:00 a.m.
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