The discharge occurred around 1:30 p.m. at the airport’s security screening area, airport officials said on Twitter.
“There is no danger to passengers or employees,” the statement said, adding the investigation remains ongoing.
An Atlanta police spokesperson confirmed no injuries had been reported as a result of the incident.
“There was an accidental discharge of a firearm near the main security checkpoint,” Atlanta police Sgt. Jarius Daugherty said. “Officers are working to determine the circumstances surrounding the incident.”
A ground stop was called for the airport for all departing flights, per the Federal Aviation Administration, but was soon lifted.
Details about the weapon or circumstances surrounding the accidental discharge have not been made available.
Witnesses recount chaos after scare
Witnesses described confusion and disarray as panic erupted in the airport’s domestic terminal. Erika Zeidler, who was traveling from Atlanta to Anchorage, Alaska, said she was sitting in Concourse T when people began running down the hallway.
“We assumed they were late for a flight,” she told CNN. “Then all of a sudden more people started running down the terminal and were screaming there was a shooter.”
Zeidler and others took shelter in a TGI Fridays restaurant, she said. Photos she shared on Twitter showed a crowd of people standing on the tarmac beneath a jetway as the incident unfolded.
Greg Romero had just gotten off a flight from Salt Lake City when he heard there was an emergency. Airport personnel “shut off all the escalators and cut off all passengers and turned off the tram,” said Romero, the father-in-law of CNN correspondent Nadia Romero.
“Right now airport personnel is doing a really good job keeping everybody calm,” he added.
A few travelers were “a little bit panicked but more frustrated,” Romero said. “They’re trying to catch flights, to get out of the airport. For the most part, people are just lined up against the walls.”
CNN’s Melissa Alonso, Nadia Romero and Ray Sanchez contributed to this report.