French authorities carried a large piece of plane debris found on the Indian Ocean island of Réunion, July 29, 2015. Reuters/Zinfos974/Prisca Bigot

The flaperon found on Reunion Island in July was "certainly" from MH370, the Malaysian plane that went missing in March 2014, French prosecutors declared Thursday. The French conclusion was reached after weeks of speculation and uncertainty concerning the origin of the wing piece.

Scientists had been testing the part to determine its origin, but examinations were delayed as one of the scientists involved in the investigation was still on vacation.

The wing was the first piece of evidence found from MH370, despite expensive and lengthy searches that spanned the Indian Ocean for more than a year. Authorities did not immediately say Thursday how the flaperon would be able to help determine what happened to the plane that fell off radar in 2014.