Cathay Pacific has confirmed that an investigation into tampering involving portable emergency oxygen bottles has resulted in the termination of two flight attendants. All crew members working on the six flights on which oxygen bottles were discovered to been emptied were suspended until being cleared by investigators. In addition to the fired employees, a number of other flight attendants not cleared for duty “continue to assist in the investigation.”

Routine inspections at Toronto Pearson International Airport (YYZ) revealed that a number of emergency portable oxygen bottles on at least two Cathay Pacific aircraft had been inexplicably discharged. When the airline launched a probe into the apparent sabotage, it was revealed that there was evidence of similar tampering later discovered on four other Cathay and Cathay Dragon aircraft as well.

Now the Hong Kong flag carrier says that two flight attendants have been fired as a result of the investigation. In a statement, the airline said that despite the firings the investigation remains active.

“The cabin crew of all concerned flights have been suspended from flight duties to facilitate the investigation process,” the airline said in a release announcing the firings. “Those who have been fully cleared have since resumed their flight duties, while some continue to assist in the investigation.”

The flights involved included the initial Hong Kong International Airport (HKG) to Toronto flights on August 17 and 18. as well as three planes on the ground in Hong Kong over the next month. In each case at least one portable emergency oxygen bottle was found depleted. In a separate incident, a crew member at Osaka International Airport (ITM) admitted to inadvertently discharging an oxygen bottle during a routine pre-flight safety check.

“Running a safe and secure operation is and always will be our greatest priority – we have robust pre-flight checks in place to identify any irregularities and to ensure all emergency equipment is serviceable so that the safety of our crew and passengers is upheld at all times,” Cathay security chief Richard Howell said in a statement “Accordingly, we have further strengthened our security measures by adding inflight and post-landing checks for all of our flights. We have communicated with our cabin crew and employees the importance of maintaining impeccable safety standards at all times. There is no compromise in this area.”

The airline said, while serious, the incidents did not put passengers at risk at any point. In each case, the oxygen bottles affected were separate from the aircraft’s built-in emergency oxygen system. Not only was the issue discovered during routine safety checks, but there were redundancies in place to ensure safe operations. Each plane involved carried between 7 and 22 bottles of portable oxygen for crew members to use in the event of an emergency – only a small fraction of those bottles were found to have been discharged.