French authorities are studying a large piece of plane debris found on Reunion Island in the Indian Ocean to determine whether it came from Malaysia Airlines Flight MH370, which vanished last year in one of the biggest mysteries in aviation history. A person familiar with the matter told Reuters the part was almost certainly from a Boeing 777, the type of aircraft operated by Malaysia Airlines on the ill-fated flight, but that it had not yet been established if it was a piece of the missing plane, Reuters reported. France's BEA air crash investigation agency said it was examining the debris, found washed up on the French island east of Madagascar on Wednesday, in coordination with Malaysian and Australian authorities, but that it was too early to draw conclusions. Nevertheless, the discovery could be the biggest breakthrough in the so-far fruitless search for MH370, which disappeared without a trace in March 2014 carrying 239 passengers and crew while en route from Kuala Lumpur to Beijing. Most of the passengers were Chinese. Aviation experts who have seen widely circulated pictures of the debris said it may be a moving wing surface known as a flaperon, situated close to the fuselage. The piece usually contains markings or part numbers that should allow it to be traced to an individual aircraft, the person familiar with the matter said. There have been four serious accidents involving Boeing 777s in the 20 years since the widebody jet came into service. Only MH370 is thought to have crashed south of the equator. Investigators believe someone deliberately switched off the plane's transponder before diverting it thousands of miles off course. Search efforts led by Australia have focused on a broad expanse of the southern Indian Ocean off Australia, roughly 3,700 km (2,300 miles) from Reunion Island.