France's air accident authority (BEA) said on Tuesday that investigator have not yet found black box of Air France 447 after a report that the French naval ships had detected signals that could be from the flight's black boxes.

No signals transmitted by the flight recorders' locator beacons have been validated up to now, the agency said in a statement.

In the context of the sea searches that are under way, work is undertaken on a regular basis that is aimed at eliminating any doubts related to any sounds that may be heard, and any findings will be made public, it said.

Jean Louis Borloo, the aid to France's top transport officials, said the black boxes have not been detected. She said on Tuesday that French military ships have heard sounds but they were not signals from the flight's voice or data recorders.

Earlier today, French newspaper Le Monde daily reported that French naval ships had detected a very weak signal from the black boxes and the mini submarine Nautile has been launched to locate the black box recorder that could contain vital clues to explain the crash.

While a spokesman from BEA said that many sounds are detected on the seabed and investigators had picked up numerous signals that had turned out to be false leads.

The Air France flight 447 crashed into the Atlantic Ocean on 1 June on its way to Paris from Rio de Janeiro with 228 people on board. The black box will stop emitting the beacon signals 30 days after the day of crash. This leaves the search team with less than 10 days to locate and recover the black box.

The Atlantic Ocean currently has been scanned for the black box of the Air France flight 447 by the French submarine Emeraude and two tug boats equipped with powerful underwater listening device provided by the U.S. Navy.

The cause of the crash is still unknown and the mystery will continue to grow until the investigators can come up with true cause of the crash.