Sailors from Brazil's navy recover debris from the missing Air France Flight 447 in the Atlantic Ocean on June 8, 2009. (Brazil Air Force/Associated Press)

The head of France's accident investigation agency said Thursday that the search will resume this month for the flight recorders from Air France Flight 447.

All 228 people on board the Airbus A330 died when it crashed in the Atlantic Ocean on June 1, 2009, while it was flying from Rio de Janeiro to Paris.

Jean-Paul Troadec, France's top aviation accident investigator, said the search area has been narrowed down to about 1,500 square kilometres, or roughly one-third of an area that is still relatively unexplored.

Troadec expects the search for the cockpit voice and flight data recorders will take several weeks.

The recorders are believed to be nearly seven kilometres under water.

Some families of crash victims have expressed frustration that the third phase of the search has not already commenced.

In a second report issued in December, BEA said they still do not know what caused the crash.

However, the investigators said the plane was likely intact when it crashed. They said oxygen masks did not drop, and the Airbus A330 did not depressurize. All of the life-vests found were still in their wrappers, suggesting passengers had little warning.