French investigators cracked open the mangled black box of a German jet on Wednesday, hoping the cockpit recordings inside would help them unlock the mystery of what caused the plane to drop unexpectedly and smash into a rugged 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 Germanwings A320 lost radio contact with air traffic controllers over the southern French Alps during a routine flight Tuesday from Barcelona to Duesseldorf before crashing. French officials said terrorism appeared unlikely, and Germany’s top security official said Wednesday there was no evidence of foul play.

Helicopters surveying the scattered debris lifted off at daybreak to eye the craggy ravine. Emergency crews, meanwhile, traveled 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 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 were zooming in on two key minutes Tuesday — 10:30-10:31 a.m. — 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, 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 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 on Wednesday that “according to the latest information there is no hard evidence that the crash was intentionally brought about by third parties.” Royal and Cazeneuve also emphasized that terrorism is considered unlikely.

The plane, operated by Germanwings, a budget subsidiary of Lufthansa, was less than an hour from landing in Duesseldorf 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 U.S. National Transportation Safety Board, said generally the voice recorder data can be downloaded in a matter of hours. She told NBC’s “Today” show the data will offer insight into “those critical minutes and seconds leading up to the crash.”

“I’m absolutely confident that the investigators are going to figure out what happened,” she said.

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 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 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 said victims included 72 German citizens, 35 Spanish, two people each from Australia, Argentina, Iran, Venezuela and the U.S. and one person each from Britain, 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 vacationing together, and 16 German high school students and their two teachers returning from an exchange program in Spain.

“Nothing will be the way it was at our school anymore,” said Ulrich Wessel, the principal of Joseph Koenig High School in the German town of Haltern.

“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,” he added.

In Spain, flags flew at half-staff on government buildings and a minute of silence was held in government offices across the country. Parliament canceled its Wednesday session.

Barcelona’s Liceu opera house held two minutes of silence at noon to honor two German opera singers — Oleg Bryjak and Maria Radner — who took the flight after performing at the theater last weekend.

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.

(AP)