Search planes and ships have located more debris from Air France Flight 447. The jet crashed into the Atlantic off Brazil's coast on Monday carrying 228 people.

Investigators fear the exact cause of France's worst air disaster may never fully emerge.

The Brazilian air force released on Wednesday the first video of the planes taking part in the search efforts.

The new debris includes what appears to be a seven-meter long chunk of the Air France jet. Brazil's air force also found 10 other metal objects and a 20-kilometer-long oil slick.

No bodies have been found and rescuers have not seen any signs of life. But the authorities are still working with the possibility of finding survivors.

The French military has also stepped up flights over the area where wreckage of the plane was spotted.

French investigators are working to probe various aspects of the case, including a review of the plane's on board systems and maintenance record.

The investigation will have its first report ready by the end of the month.