Federal authorities and Delta Air Lines officials are investigating a serious security breach involving a flight from Mexico at Hartsfield-Jackson International Airport, Channel 2 Action News reported.

The incident happened Sunday night after a Delta flight arrived in Atlanta from Cancun. Dozens of passengers were allowed to leave the plane and go directly to the baggage claim area in the new International Terminal without first clearing customs or immigration.

"We didn't go through customs. We didn't go through security. Something's not right," passenger Bonnie Beck told Channel 2. "We saw a group of people from our flight, and they looked just as confused as we did."

Passengers were able to go straight into Concourse E and bypass customs and immigration, authorities said. Airport personnel quickly spotted the error.

"Somebody from the airport comes running over, screaming, 'Were you on the Cancun flight? If so, you need to come with me right now!'" Beck said.

Monday, Delta was working with customs and border protection agents to reach three passengers who left the airport without clearing customs and immigration.

The three passengers were found and were screened and cleared, Channel 2 reported Tuesday.

In an emailed statement, Delta spokesperson Morgan Durrant said, "Delta regrets the error and the inconvenience, however, the safety and security of our customers is Delta's number one priority. We continue to investigate the episode."

Atlanta security expert Brent Brown told Channel 2 that the incident was a major mistake.

"If you let anybody out or if you don't control that environment, then security is breached. And once the breach starts, you can't control the area at all," Brown said.