TSA agents allowed a convicted felon and former member of a domestic terrorist group to pass through an expedited security line , Homeland Security 's internal watchdog has revealed . The passenger , whose identity has not been released , has served years in prison for murder and offenses involving explosives , the Department of Homeland Security's Inspector General 's Office said as it revealed the 'significant aviation security breach ' in a statement on Thursday night . The watchdog was asked to investigate the June 2014 incident last October after a whistleblower came forward . It did not release specific details of the passenger 's criminal history or where the incident took place . The passenger , who is a U.S. citizen , had not registered for the TSA 's PreCheck program , but if they had , they would have been rejected because of their convictions , the office said in the statement . 'Significant security breach ' : A passenger who has convictions for murder and offenses involving explosives was allowed to pass through the TSA 's PreCheck line ( file picture ) despite an agent recognizing them . Instead , they were selected for the screening through the Secure Flight program 's 'risk assessment rules ' , the watchdog said . The program compares information the traveler has given their airline with information from the Terrorist Screening Database , No Fly lists and other intelligence-based systems to determine if they can board the plane and to identify low-risk passengers for expedited screening . After determining a passenger can be pre-screened , it allows them to print documents carrying the PreCheck sign . The TSA was unable to show the traveler 's vetting results because they are deleted seven days after travel , the Inspector General 's Office said . When the passenger reached the airport , an agent looked at their documents . 'After checking the traveler 's boarding pass and identification , an alert Transportation Security officer at the airport recognized the felon and alerted his supervisor , ' the watchdog said , CNN reported . 'However , the supervisor directed the [ officer ] to take no action and allow the traveler to continue through the TSA pre-check lane . ' As part of the PreCheck system , the passenger - who has a criminal history involving explosives - would not have had to take off their shoes or jackets or remove liquids from their carry-on luggage . Investigation : The TSA responded that all passengers , including those with PreCheck tickets , are subject to 'robust ' checks . It is not known where the June 2014 breach took place . The incident was brought to the attention of the Inspector General 's Office 's after a whistleblower went to the U.S. Office of Special Counsel , an independent federal investigative agency . A classified report was issued to TSA detailing the need to make changes to the PreCheck vetting and screening process . On Thursday , the TSA said in a statement that it 'takes its responsibility for protecting the traveling public very seriously ' . 'All passengers , including those with TSA PreCheck on boarding passes , are subject to a robust security approach that employs multiple layers of security , both seen and unseen , ' it said . The TSA added that the success of its pre-screening system relies on the intelligence and national law enforcement communities identifying passengers they believe to pose a risk - yet this passenger had not been place on one of their lists . Still , the agency said it was reviewing the guidelines it provides to TSA officers and supervisors to ensure they 'clearly understand the procedure in the event a person or item presents a creditable threat to transportation security ' .
The unidentified passenger had convictions for murder and offenses related to explosives , said Inspector General 's Office Homeland Security 's . Despite this , the traveler was issued a ticket allowing them to take the PreCheck lane . A TSA agent recognized the felon and told their supervisor - but the supervisor allowed the passenger to go through anyway . PreCheck means passengers can keep on their jackets , do not need to remove shoes and do not need to take liquids out of their luggage . The watchdog , which began investigating in October after a whistleblower came forward , did not say where the June 2014 incident took place . TSA said it takes its responsibility to protect the public 'very seriously '