Paris - An investigation into the cause of the Air France disaster was formally opened in France Wednesday, as the country began a period of national mourning with a service for the dead in Notre Dame Cathedral. President Nicolas Sarkozy and other government members will attend the memorial service in Paris later Wednesday at the cathedral.
Meanwhile an investigation was formally opened into the crash, after fragments found in the Atlantic Ocean were confirmed as debris from the Airbus A330-200 aircraft, which was carrying 228 people.
The investigation into the world's worst commercial air disaster since 2001 was formally opened just hours after Brazilian Defence Minister Nelson Jobim said there was "no doubt" that the debris discovered belonged to the Air France flight that vanished early Monday on a flight from Rio de Janeiro to Paris.
The fragments - metal pieces and wires, apparently part of the structure of the missing plane, and a passenger seat - were found by Brazilian army planes late Tuesday some 640 kilometres off the island of Fernando de Noronha.
Two investigators from the French Office of Investigations and Analysis (BEA) were already in Brazil when the debris was found. The BEA is to head the enquiry in colloboration with its counterpart Brazilian agency CENIPA.
Early Wednesday, the French military said in a statement that "there could be no doubt" that the debris belonged to the missing airliner, even if formal identification remained to be carried out.
Captain Christophe Prazuck, of the French army chief of staff, said that Wednesday would be "a day of transition" in the search for the aircraft.
"We will move from an air operation covering a large zone to a naval operation over a restricted zone," he was quoted as saying by the online edition of the daily Le Figaro.
The merchant ships and navy vessels in the area will gather the debris floating on the surface before submarines are deployed in the coming weeks to search for the wreckage itself, he said.
In addition an Awacs surveillance plane will carry out a "cartography" of the debris in an attempt to determine the precise place where the aircraft crashed into the sea, to enable the eventual recovery of the plane's black box flight data recorders, Prazuck said.
With the site of the crash now established, attention has turned to commemorating the victims.
As well as the Paris memorial service, late Tuesday, the Brazilian government declared three days of mourning for the crash victims.
There were 72 French nationals, 60 Brazilians and 26 Germans among the 228 people on the plane.
