Newark, New Jersey (CNN) -- A security breach at Newark Liberty International Airport Sunday evening forced the closure of a terminal for hours while authorities rescreened thousands of passengers.
The incident happened at about 5:20 p.m. at Terminal C, when a man walked through an exit on the public side to the secure "sterile" side for passengers who had cleared screening, according to the Transportation Security Administration.
"Rescreening began after the Port Authority Police and TSA swept each of the concourses in the terminal with negative findings," said Ann Davis, a TSA spokeswoman.
"The man in question was never located; however, TSA's rescreening effort will ensure that every passenger boarding an aircraft tonight out of Newark's Terminal C has been fully screened."
All passengers had been rescreened by early Monday, according to the TSA. Flights from Terminal C were grounded until the process was completed.
Authorities reviewed video from airport cameras but were not sure whether the man was once on the sterile side and went back or if he never went through screening, Davis said.
The incident caused arrival delays and mainly affected Continental Airlines, which is the airport's largest tenant.
CNN's Alina Cho, who arrived at the airport Sunday night on a flight from Fort Lauderdale, Florida, described a hectic scene, saying many passengers who had already boarded outgoing flights had to get off planes to be rescreened.
"I just saw one woman pleading with a gate agent, saying that she had two small children and a heart condition -- that she simply could not take this," Cho said. "But of course, there will be no exceptions."
Newark Liberty International Airport, which is about 15 miles from Manhattan, is the second-largest hub for Continental.
The airport handles about 35 million passengers a year.
CNN's Susan Candiotti and Ross Levitt contributed to this report.