Travelers walk into US customs at Hartsfield-Jackson International Airport in Atlanta.
CNN  — 

The Transportation Security Administration has started an investigation after an official said a gun may have been missed during a security check at Hartsfield-Jackson Atlanta International Airport.

A government official with knowledge of the incident told CNN that an Atlanta airport passenger might have boarded a plane on Tuesday carrying a bag with a gun.

A carry-on bag screening detected an item on Tuesday that may have been a firearm, said the official, who spoke on the condition of anonymity. The bag did not set off an alarm when it was run a second time through the screening device, and the passenger was allowed to leave the checkpoint with the bag.

TSA has not definitively identified the item and does not know the identity of the passenger.

“This is a one-in-a-million,” the official said.

What happened at the airport

TSA said in a statement “there are unconfirmed reports of a missed firearm at the South TSA checkpoint at Hartsfield-Jackson Atlanta International Airport.”

“As a prudent security measure, TSA scanned the terminal for the passenger with the carry-on bag in question,” the statement said.

The official said TSA discovered the issue later during a routine review of screening technology images.

“By the time they saw it, the passenger was probably on a flight,” the official said.

While the investigation is ongoing, the official said the preliminary indication is that the bag was set aside after triggering the alarm, but it was not properly moved for a more detailed hands-on screening.

TSA Spokesman Carter Langston told CNN the incident is under investigation.

Guns being found ‘at an alarming rate’

The agency said in its statement that its officers are finding guns “at an alarming rate at checkpoints.” Last year set a record for firearms caught at checkpoints – even though fewer people were traveling because of the pandemic.

“I think more people are carrying weapons, just generally across the country, and then whatever is happening across the country we see reflected in our checkpoints,” TSA Administrator David Pekoske told CNN in an interview at the time.

Penalties for bringing a gun to a checkpoint range up to about $13,000.

Top image: Travelers walk into US customs at Hartsfield-Jackson Atlanta International Airport. (Camilo Freedman/SOPA Images/LightRocket/Getty Images)

Clarification: This story has been updated with new information clarifying that details of the incident are preliminary and part of an ongoing investigation.