Once Sunday's breach was confirmed by TSA after 7 p.m., security screening stopped as an attempt was made to locate the man who had passed through the wrong door. Moments later, it was decided to remove all passengers from Terminal C -- the airport's busiest -- so that officers could search the concourse and every passenger could be rescreened.
The TSA officer stationed at the exit door as been reassigned.
"The officer has been assigned to non-screening duties pending a review of the breach," the TSA's Ann Davis said. "TSA will look at all of the circumstances and make a determination as to what level of disciplinary action is warranted."
U.S. Sen. Frank R. Lautenberg, D-N.J., plans to question the nation's top aviation security officials about this incident at a hearing Jan. 20.
"The TSA's failure to prevent someone from walking into a secure area of Newark Liberty Airport is completely unacceptable. This security breakdown was inexcusable, especially when our aviation system was supposedly on high alert," Lautenberg said in a statement. "TSA must immediately conduct a full investigation to determine what went wrong and make sure it never happens again so that air passengers feel confident every time they board a plane."
It took several hours to sweep the empty Newark concourse Sunday night. Passengers were allowed to go back through security just before midnight.
"We had to take action that unfortunately inconvenienced a hell of a lot of people," Davis said.
Continental says more than 100 flights were impacted, and though the operation is "looking good" today, there are still some international flights that were behind schedule Monday afternoon.
"We're going to look at the timeline to see how we could have done better," Davis said.
The offending man has still not been identified and has not been found. Surveillance cameras showed him leaving the airport 20 minutes after he breached the exit door. Nothing harmful was discovered during the security sweep.
These kinds of episodes happen on occasion, the TSA says. In the week that began Dec. 14, the agency says there were 37 incidents at airports across the country that involved a checkpoint closure, terminal evacuation or a sterile area breach.
Sunday's breach at Newark comes as the TSA implements new security procedures or passengers flying into the US from countries tied to terrorism, in the wake of the attempted Christmas day bombing of a plane headed to Detroit.
Passengers on flights arriving from Paris and Mumbai told ABC News they were frisked at their departure gates, and every piece of their carry-on luggage was searched.
"You had to take off your jacket, you had to take off your purse, they went through your purse and did the whole body thing," one passenger said.