European regulators have pinpointed a potentially flawed cleaning process during maintenance as investigators probe an engine fire that caused a Cathay Pacific Airbus jet carrying 348 people to turn back to base.

The EASA has issued an updated Airworthiness Directive after a cleaning process was found to be linked to a Cathay A350-1000 engine fire.

Hong Kong's air safety authority said Thursday that a defect in an engine component of a Cathay Pacific Airways Airbus A350 that caused a fire, forcing a Zurich-bound flight to return to Hong Kong, could have caused ''extensive damage'' to the aircraft.