French investigators have formally identified a washed-up piece of airplane debris found in July on a remote island in the Indian Ocean as part of Malaysia Airlines Flight 370, a Boeing 777 that disappeared more than a year ago with 239 people aboard.

Investigators have been examining the wing part, called a flaperon, since it was flown to a French aeronautical research laboratory near Toulouse last month. Malaysian authorities had already declared that the wing fragment was from the missing jet, but until now French investigators couldn't say with certainty that it was the case.

The Paris prosecutor's office said in a statement Thursday that investigators used maintenance records to match a serial number found on the wing part with the missing Boeing.

"Today it is possible to state with certainty that the flaperon discovered on Reunion July 29, 2015 corresponds to that of Flight MH370," the prosecutor's statement said.

The flight's disappearance on March 8, 2014, has been one of aviation's most confounding mysteries.

Until the wing flap washed ashore July 30 on the French island of Reunion, investigators had not found a single physical clue linked to the missing plane, despite a massive air and sea search. Officials believe it crashed in the southern Indian Ocean, killing everyone aboard, but are unsure of the cause.

The discovery of the wing flap refocused the world's attention on the investigation, which many hope will finally yield clues to the plane's fate.

Australian forces are continuing their search for the plane in a desolate stretch of ocean 4,200 kilometers (2,600 miles) to the east of Reunion, where experts believe the plane from Kuala Lumpur to Beijing crashed.

Investigators examining the wing fragment in France are trying to glean clues into the plane's fate based on its condition, opening up even more questions: How, exactly, did the plane end up in the water? Was it a controlled landing? Was there an explosion?

Officials who scrutinized data exchanged between the plane's engine and a satellite determined that the jetliner took a straight path across the ocean, leading them to believe that the plane flew on autopilot for hours before running out of fuel and crashing into the water.