TSA immediately halted screening at Terminal C's security checkpoints.
TSA and other law enforcement agencies began reviewing video tape to try to identify the individual.
While the Port Authority Police continued to look for the individual, TSA and the PAPD cleared the "sterile" side of Terminal C and began moving all travelers back to the "public" side of the terminal for rescreening.
"This effort will ensure that every passenger boarding an aircraft tonight out of Newark's Terminal C has been fully screened," TSA spokesperson Ann Davis said.
The breach caused major problems for travelers at the airport. Photos from Twitter users inside the terminal (http://twitpic.com/wks45) showed huge crowds as passengers were moved and rescreened.
New travelers arriving at the terminal were kept in the arrivals area and some were spilling over on top the apron outside the terminal.
"If they find the guy who is responsible for all this, he's going to be in trouble," said Army Pvt. John Davis.
Davis was due back at his base in Seattle by 6:00 Monday morning.
Alison Day, 47, of York, England, was supposed to leave for Manchester, England, at 7:30 Sunday night. She was traveling with a party of seven including an 18-month-old and 5-year-old.
"I'm not angry that this is happening, but I'm angry that there was a lack of organization," she said.
She said her party, headed home after a Caribbean cruise, was escorted out of Continental's lounge but given no further instructions.
As of 11:00 p.m., flights were still not allowed to leave from Terminal C.
That caused a ripple effect, as incoming planes had nowhere to park. Numerous people using Twitter reported sitting on planes for more than an hour after landing. The FAA also issued a ground stop for departures to Newark.
The terminal serves Continental and Continental Express.
Continental is providing the option for travelers to re-schedule or re-route, without penalty. You can find more information on Continental's website at www.continental.com/web/en-US/content/news/travelnotices.aspx.