At least part of Airbus's A350 fleet will be inspected as a precautionary measure, Europe's aviation safety regulator said on Thursday, after an engine part failed during the flight of a Cathay Pacific A350-1000 passenger plane.

Barring fresh evidence as investigators examine the fuel system of a jet forced to return to Hong Kong on Monday, manufacturers had been leaning against recommending worldwide checks, sources told Reuters on Wednesday.

"We will require a one-time fleet inspection, which may be applicable only to a portion of the A350 fleet, in order to identify and remove from service any potentially compromised high pressure fuel hoses," the European Union Aviation Safety Agency (EASA) said in a statement.

EASA will release an airworthiness directive with details of the inspection later on Thursday, it added.

"We acknowledge the information provided by EASA and are working closely with (engine maker) Rolls-Royce and the authorities on the implementation of this precautionary measure," Airbus said.

Rolls-Royce did not immediately respond to a request for comment.

Airbus and Rolls-Royce briefed airlines on the fallout from the issue earlier on Thursday, sources familiar with the matter said.

The A350-1000, the larger of two models in the Airbus A350 family, and its Rolls-Royce XWB-97 engines have been under the spotlight since a Zurich-bound jet was forced to return to Hong Kong after an engine problem, later traced to a fuel leak.

Initial investigations have revealed that a flexible pipe feeding a fuel injection nozzle in the XWB-97 engine was pierced, the sources said.