Investigators 'know' it comes from a Boeing 777 but they still need to identify a number inside wing part to confirm it is missing jet.
The largely fruitless search of waters off Indian Ocean island began after a wing section apparently from lost plane was found there last month.
Boats and helicopters are also being deployed off the Indian Ocean island to expand the hunt for missing Malaysia Airlines plane.
Serge Mackowiak was more cautious than Malaysian prime minister about origins of wing part found on France's Réunion island.
Identification of aircraft part found on Réunion island last week could be first clue to fate of missing Malaysia Airlines flight.
Officials from Malaysia, China, Australia and France hold meeting in Paris to discuss progress of investigation into missing plane.
Aircraft wing part washed up on Réunion will be driven to Toulouse defence laboratory for confirmation it belonged to missing Boeing 777.
French air accident investigators in Toulouse will examine wreckage amid growing speculation it is from the missing Malaysian airliner.
Possible wing debris found on Indian Ocean island of La Réunion is being examined to see if it comes from doomed 2014 Malaysia Airlines flight.