When Air France flight 447 disappeared en route from Rio de Janeiro to Paris on June 1, 2009, all 228 people on board were killed, and the debris was strewn over the Atlantic Ocean. Now, in the robot-assisted fourth round of searches for any remnants of the crash, French investigators say they have found more pieces of the jet.

The BEA, the French agency that investigates air accidents, has not yet identified which parts of the plane were found, or what caused the crash, CNN reports.

In the initial search for bodies and debris immediately following the crash, less than a quarter of the bodies were located, and neither of the plane's two black boxes were recovered.

"It's like trying to find a shoe box in an area the size of Paris, at a depth of 3,000m (9,800ft) and in a terrain as rugged as the Alps," French navy spokesman Hugues du Plessis d'Argentre told AFP of the search for the flight recorders in May 2010.

Unmanned submarines have now been deployed in the search, which has been criticized by victims' families for a lack of results. Airbus and Air France are funding the ongoing search for information about what could have caused the plane to fall.

"We do hope that the discovery will lead to the retrieval and reading of the two recorders because this data is essential for the understanding of this accident," a spokesman for Airbus, which built the downed jet, told The Guardian.

Airbus and Air France are the subjects of a French criminal investigation of the crash.

Image via WikiMedia Commons.