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.

A cleaning process leading to fuel hose degradation during refurbishment may have caused a recent Airbus A350 engine fire that triggered dozens of Cathay Pacific flight cancellations this month, the EU aviation regulator said Thursday.

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.