Terminal C at Newark Liberty International Airport was locked down for three hours Sunday, creating a huge screening backlog that forced the cancellation or delay of more than 165 flights, after officials said a passenger prematurely walked away from a security checkpoint.

Authorities searched for the female passenger based on a checkpoint surveillance video following the 8:45 a.m. incident said Al Della Fave, a spokesman for the Port Authority Police.

Local officials of the Transportation Security Administration eventually concluded the woman had boarded a United Airlines flight to Cleveland. But the security agency only arrived at its conclusion after the flight had landed in Cleveland at 10:45 a.m., and authorities were never able to talk to the woman or identify her by name.

“She walked out of the checkpoint area before the screening process was complete,” Ann Davis, a TSA spokeswoman, said in a statement. “Management at Newark will conduct a comprehensive review of the incident and will take appropriate action.”

Normal screening operations at Terminal C resumed at about noon. But the lockdown and subsequent screening backlog caused more than 65 departing flights to be delayed, and more than 100 flights to be canceled, said Christen David, a United spokeswoman.

Travelers stranded after Newark airport security breach cancels more than 100 flights.  Oh they weren’t finished yet.

There was one other breach reported at Terminal C Sunday.

newark-airport.jpgPassengers wait to go through security at Newark Liberty International Airport this morning.

At 6:30 a.m., the TSA said operations were suspended in the oversize baggage screening room, after a bag was directed onto the tarmac despite not having been completely screened. Bag screening resumed at 7:19 a.m., the TSA said. But the flagged bag, which was isolated on the tarmac, was not cleared for another two hours, after the Essex County Bomb Squad gave its okay.

Officials said the lockdown forced some flights back to the gate after they had taxied for takeoff, in order for authorities to visually check passengers in their search for the woman who had walked away from the checkpoint.

And now they get a crack at unionization.