(Reuters) – A passenger boarded a Delta Air Lines flight from New York to Paris without a ticket, somehow evading two boarding pass checks and leading both Delta and the U.S. Transportation Security Administration to say they were investigating how it happened.

French police boarded the plane in Paris and took the stowaway into custody on Wednesday before the other passengers were let off the plane, CNN reported, citing a ticketed passenger who was onboard.

Delta Flight 264 left New York’s JFK Airport on Tuesday night and landed at Paris’ Charles de Gaulle Airport on Wednesday.

TSA said the person was physically screened before the flight and boarded without any prohibited items.

“The individual bypassed two identity verification and boarding status stations and boarded the aircraft,” TSA said in a statement, adding, “TSA will independently review the circumstances of this incident at our travel document checker station at JFK.”

Passengers typically pass through at least two boarding pass checks: one at the TSA screening checkpoint before entering the boarding area and another by the airline at the gate.

“Nothing is of greater importance than matters of safety and security. 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,” Delta said in a statement.

(Reporting by Daniel Trotta; Editing by Bill Berkrot)