Eleven passengers were allowed to pass through a Transportation Security Administration (TSA) checkpoint at Kennedy International Airport on Monday without first being screened, the New York Daily News reports.

The passengers were able to do so, because the TSA left the area open without any officials to keep watch. A security video reportedly shows a metal detector going off as the people pass through.

TSA didn’t report the incident to police until two hours after the it occurred. After law enforcement was notified, police flooded the airport terminal in search of the passengers, but they were not found, according to the Daily News.

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An investigation into the incident is ongoing and law enforcement is continuing to look for the passengers, sources told the Daily News.