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A Delta aircraft as seen on final approach for landing in New York John F. Kennedy International Airport.
CNN  — 

Investigators are trying to determine how a woman got past multiple security checkpoints this week at New York’s JFK International Airport and boarded a plane to Paris, apparently hiding in the aircraft’s bathrooms during the flight.

The stowaway didn’t have a boarding pass but completed a security screening and bypassed two identity verification and boarding status stations to board a Delta aircraft, according to the Transportation Security Administration.

The Tuesday incident happened on one of the busiest travel days of the year. Nearly 2.7 million passengers traveled on airplanes that day, ahead of the Thanksgiving holiday, according to TSA data.

Here’s what we know:

‘Exhaustive investigation’ underway

The stowaway was not carrying any prohibited items, according to a TSA spokesperson.

It’s unclear how the individual was able to bypass boarding stations before getting on the plane.

Delta is working with law enforcement and conducting an investigation of its own, the airline said.

“Nothing is of greater importance than matters of safety and security,” a Delta spokesperson said in a statement. “That’s why Delta is conducting an exhaustive investigation of what may have occurred and will work collaboratively with other aviation stakeholders and law enforcement to that end.”

CNN has reached out to the FBI and Customs and Border Protection for more information.

Stowaway is a US green card holder

The stowaway is a woman between 55 and 60 years old and has a Russian passport, according to an airport official in Paris. She will soon be sent back to the United States, the official said.

The woman was in a waiting zone at Charles de Gaulle airport - known as ZAPI - for people awaiting deportation, as she does not meet the conditions for entering Europe. The woman applied for asylum in France a few years ago, the official told CNN.

When asked, the source did not address the woman’s mental state.

When the woman is sent back to the US, the TSA could issue a civil penalty and New York authorities could arrest her, although they are not currently involved, a federal official familiar with the investigation told CNN. The TSA is conducting its own investigation of the incident, the official noted.

Pilot made an announcement about ‘a serious security issue’

New York City real estate broker Rob Jackson was on the Delta flight when the stowaway was discovered and told CNN that passengers were told to stay seated after landing so police could board the plane.

“I didn’t actually see the person in question. Apparently she hid in a lavatory all the way at the rear of the aircraft when we departed JFK,” Jackson said. “The first announcement to passengers that there was a problem was when we parked at the gate and they instructed us all to remain seated because French police were going to board the aircraft to deal with ‘a serious security issue.’”

Jackson recorded a video in which the flight captain can be heard saying: “Folks, this is the captain, we are just waiting for the police to come on board. They may be here now and they directed us to keep everyone on the airplane until we sort out the extra passenger that’s on the plane.”

The flight was full and there were no extra seats for the stowaway, Jackson said.

“I overheard the flight attendants talking about it with the pilots – they said this person was in one lavatory and then would exit and walk to a different lavatory and go in there for a long time,” he said.

CNN’s Lex Harvey and Saskya Vandoorne contributed to this report.