Nearly a dozen passengers slipped by an unattended TSA PreCheck checkpoint at Kennedy Airport early Monday morning, a law enforcement source said.

The 11 passengers were able to walk through the Terminal 5 checkpoint about 6 a.m., the source said.

Port Authority Police were notified of the breach by a TSA supervisor about two hours later, the source said, but were not able to find the passengers.

TSA spokesman Nico Melendez said the agency was “reviewing reports of a possible security incident” and that early reports indicated that three passengers didn’t receive “required secondary screening” after setting off an alarm in the walk-through metal detector.

Three of the unscreened passengers were identified on video and boarded a flight to California, the source said.

The TSA “conducted security measures” at the arrival airport, Melendez said.

Federal and state authorities are still working to identify the other eight passengers, who the source said are believed to have boarded various flights.

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Melendez said all carry-on bags were properly screened, and a K-9 team was present at the checkpoint at the time.

“[The] TSA works with a network of security layers both seen and unseen,” Melendez said. “We are confident this incident presents minimal risk to the aviation transportation system. Once our review is complete, TSA will take appropriate action.”

In an earlier statement the TSA had said employees will be disciplined and retrained “as appropriate” once the review is completed.

Sen. Charles Schumer said the TSA has to “come up with a fail proof system” to prevent a similar incident from happening again following a full investigation.

“This security breach is inexcusable,” Schumer told reporters. “To have people go through the security lines unchecked, and then for TSA not to alert the Port Authority for two hours — can you imagine what could happen within two hours? The TSA has to tighten things up.”