The search for the cockpit voice and flight data recorders of the Air France Airbus A330 that crashed in the Atlantic Ocean while flying from Rio de Janeiro to Paris on June 1 has been delayed by weather conditions and trouble getting a specialized search ship to Brazil.

In a statement, the French accident investigation agency BEA blamed "administrative and technical difficulties" along with the poor weather conditions for the delay in starting the third phase of the search.

French aviation investigators have expressed cautious optimism about finding the black boxes of Air France Flight 447, which crashed in the Atlantic last June en route from Rio de Janeiro to Paris. All 228 people aboard the plane were killed.

The third search was organized after two earlier efforts failed to locate the jetliner's FDR and CVR.

Jean-Paul Troadec, chief of the French Accident Investigation Agency, said an international team of experts have reduced the search area to 965 square miles, a fifth the size of the previous Atlantic Ocean search zone.

The U.S. Navy and the U.S.. National Transportation Safety Board are assisting in the search, along with accident experts from Britain, Germany, Russia and Brazil. Private companies are also involved, providing mini-subs and boats equipped with sonar gear.

The new search has a budget of $13.73 million. The new search is jointly financed by Airbus and Air France. The search site includes depths of up to 4,000 meters.

The black boxes are no longer emitting locator signals, but officials are optimistic the submarines and boats equipped with sonar gear will be able to find the wreckage.

Jean-Paul Troadec, put the odds of finding the downed plane and its flight data recorders at "well above 50 percent."

Investigators used computer models of currents and wind direction in the days after the crash to narrow the search zone under scrutiny. "We have reduced the size of the haystack," Troadec said. "Now we have to find the needle."

The new hunt is set to last four weeks, but could be extended, provided additional funding can be obtained.