French investigators are hoping cockpit recordings from the "black box" retrieved from the crashed Germanwings passenger jet will unlock the mystery of what caused the plane to drop unexpectedly before smashing into an Alpine mountain, killing all 150 on board.
The orange cockpit voice recorder - dented, twisted and scarred by the impact - is considered the key to understanding why the A320 aircraft lost radio contact with air traffic controllers over the southern French Alps during Tuesday's routine flight from Barcelona to Dusseldorf before crashing.
French officials said terrorism appears unlikely, and Germany's top security official said there is no evidence of foul play.
Helicopters surveying the scattered debris lifted off at daybreak to eye the craggy ravine. Emergency crews, meanwhile, travelled slowly over the steep, rocky terrain to the remote high-altitude crash site through snow and rain.
The crash left pieces of wreckage "so small and shiny they appear like patches of snow on the mountainside," said Pierre-Henry Brandet, the French interior ministry spokesman, after flying over the debris field.
French interior minister Bernard Cazeneuve told RTL radio the "black box is damaged and must be reconstituted in the coming hours in order to be useable".
Investigators are zooming in on two key minutes on Tuesday - 10.30-10.31am local time - said Segolene Royal, a top government minister whose portfolio includes transport.
From then on, air traffic controllers were unable to make contact with the plane.
The voice recorder takes audio feeds from four microphones within the cockpit and records all the conversations between the pilots and air traffic controllers as well as any noises in the cockpit.
Photos released by France's air accident investigation agency appeared to show the cylinder that holds the memory apparently intact.
The flight data recorder, which Mr Cazeneuve said has not been retrieved yet, captures 25 hours' worth of information on the position and condition of almost every major part in a plane.
German interior minister Thomas de Maiziere told reporters in Berlin that "according to the latest information there is no hard evidence that the crash was intentionally brought about by third parties."
Ms Royal and Mr Cazeneuve also emphasised that terrorism is considered unlikely.
The plane, operated by Germanwings, a budget subsidiary of Lufthansa, was less than an hour from landing in Dusseldorf when it unexpectedly went into a rapid eight-minute descent. The pilots sent out no distress call, France's aviation authority said.
Lufthansa CEO Carsten Spohr, himself a pilot, said he found the crash of a plane piloted by two experienced captains "inexplicable".
Investigators retrieving data from the recorder will focus first "on the human voices, the conversations" followed by the cockpit sounds, French transport secretary Alain Vidalies told Europe 1 radio.
Deborah Hersman, president and CEO of the National Safety Council and a former chair of the US National Transportation Safety Board, said generally the voice recorder data can be downloaded in a matter of hours. She said: " I'm absolutely confident that the investigators are going to figure out what happened."
Bereaved families made their way to the southern French Alps, as did the leaders of France, Germany and Spain, since most of the passengers were German and Spanish.
French president Francois Hollande and German chancellor Angela Merkel arrived at a village near the crash site by helicopters on a mountain meadow whipped by strong wind. Spanish prime minister Mariano Rajoy joined them at the scene in the French town of Seynes-les-Alpes.
Lufthansa said two charter flights to France will be made available for family members who want to get as close as they can to the crash site.
Locals in Seyne-les-Alpes offered to host the bereaved families because of a shortage of rooms to rent.
Germanwings itself cancelled several flights on Wednesday because some crews declared themselves unfit to fly after losing colleagues.
"The management completely understands this because we are a small family. Everyone knows everybody inside Germanwings, so it is a big shock for employees," said CEO Thomas Winkelmann.
He said the company had already contacted the families of 123 victims and was trying to reach relatives of the remaining 27.
He added that victims included 72 German citizens, 35 Spanish, two people each from Australia, Argentina, Iran, Venezuela and the US, and one person each from the UK, the Netherlands, Colombia, Mexico, Japan, Denmark, Belgium and Israel. Some could have dual nationalities.
They included two babies, two opera singers, an Australian mother and son holidaying together, and 16 German high school students and their two teachers returning from an exchange programme in Spain.
Ulrich Wessel, the principal of Joseph Koenig High School in the German town of Haltern, said: "Nothing will be the way it was at our school any more.
"I was asked yesterday how many students there are at the high school in Haltern, and I said '1,283' without thinking - then had to say afterward, unfortunately, '16 fewer since yesterday'. And I find that so terrible."
In Spain, flags flew at half-mast on government buildings and a minute of silence was held in government offices across the country. Parliament also cancelled its Wednesday session.
Barcelona's Liceu opera house held two minutes' silence at noon to honour two German opera singers - Oleg Bryjak and Maria Radner - who took the flight after performing at the theatre the weekend before.
In an eerie coincidence, an Air France flight from Paris to Saigon crashed close to the same spot in the French Alps in 1953, killing all 42 people on board.
Remi Jouty, director of the French aviation investigative agency, said some audio had been recovered from the recorder, including sounds and voices.
He said it was too early to draw any conclusions from the recorder, which takes audio feeds from four microphones in the cockpit and records all the conversations between the pilots, air traffic controllers as well as any noises.
Mr Jouty said the plane was flying "until the end".
He said the final communication from the plane was a routine message about permission to continue on its route.
French president Francois Hollande, meanwhile, said the case for the plane's second black box had been found, but not its contents.
That was the flight data recorder, which captures 25 hours' worth of information on the position and condition of almost every major part in a plane.
"At this moment people are on the scene still searching," he said, speaking alongside German chancellor Angela Merkel and Spanish prime minister Mariano Rajoy in Seynes-les-Alpes.
"This is a true tragedy, and the visit here has shown us that," Ms Merkel said.
Mr Hollande promised that French investigators would do everything to determine the crash's cause.