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 Hong Kong aviation investigation revealed Cathay Pacific's Airbus A350 engine failure was due to a ruptured fuel hose. The incident highlighted potential risks of engine fires caused by fuel leaks.

European regulators have widened the number of Rolls-Royce Trent engines affected by a potential fuel hose defect, in an updated directive issued 19 September following an engine fire on a Cathay Pacific Airbus A350-1000.

The European Union Aviation Safety Agency (EASA) on Thursday gave an update on the inspections it ordered on Rolls-Royce-made engines used in Airbus A-350 aircrafts following a security incident, pointing to issues possibly stemming from a cleaning process.

While the initial emergency directive applied only to the Airbus A350-1000 engine, the latest AD was extended to all Airbus A350 engines.