LONDON- Investigators probing an engine explosion on an Air France A380 in 2017 are studying a possible manufacturing flaw with a key part in a move likely to trigger checks on dozens of Airbus superjumbos worldwide, people familiar with the matter said.

The focus of a two-year-old investigation into the mid-air explosion over Greenland, which left the plane carrying more than 500 passengers with the front of one engine missing, has switched to the recently salvaged "fan hub," the people said.

The titanium part is the centrepiece of a 3-metre-wide fan on engines built for the world's largest airliner by U.S.-based Engine Alliance, co-owned by General Electric GE.N and United Technologies unit Pratt & Whitney .

It had sat buried in Greenland's ice sheet since September 2017 when one of four engines on Air France flight 66 abruptly disintegrated en route from Paris to Los Angeles. It was prised from the ice in June after a high-tech aerial radar search.

Following a microscopic analysis, Engine Alliance is expected to order airlines to carry out checks for any flaws on similar parts in its engines, which power some 60 percent of the 237 A380s in service, the people said.

The suspect part was fabricated under the auspices of Pratt & Whitney, which declined to comment.

France's BEA air accident agency, which is leading the investigation, declined to comment.

Engine Alliance is one of two engine suppliers for the Airbus A380 in competition with Britain’s Rolls-Royce .

Besides Air France, other airlines operating the A380 with Engine Alliance powerplants include Dubai's Emirates, Qatar Airways, Abu Dhabi-based Etihad and Korean Air.

It was not immediately clear what sort of checks would be required, nor whether they would involve taking planes out of service outside their usual maintenance schedules.

Experts say detecting metallurgical flaws deep inside the titanium alloys used for such parts can be challenging.

Investigations are not yet complete and are likely to tackle other factors such as the loads or physical forces at play on the engine and the giant double-decker jet's wing structure.

Safety experts say air accidents are rarely caused by isolated factors.

Europe's Airbus declined comment.

(Reporting by Tim Hepher; Editing by Sudip Kar-Gupta) ((tim.hepher@thomsonreuters.com; +33 1 49 49 54 52; Reuters Messaging: tim.hepher.thomsonreuters@reuters.net))