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.

The European Union Aviation Safety Agency (EASA) also said it had widened the number of engine variants potentially affected by the suspected defect, which include Rolls-Royce engines powering A350-900s and A350-1000s.

Hong Kong-based Cathay briefly grounded its fleet of A350s for inspections and repairs after a Zurich-bound plane was forced to head back to the Chinese city on September 2.

Inspections found that components on 15 of the 48 planes in the fleet of A350s, powered by engines from the British manufacturer Rolls-Royce, had to be replaced.

The results of a Hong Kong probe released Thursday said the Zurich-bound plane's engine defect could have escalated into "extensive damage".

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