SEYNE-LES-ALPES, FRANCE—A black box recovered from the scene and pulverized pieces of debris strewn across Alpine mountainsides held clues to what caused a German jetliner to take an unexplained eight-minute dive Tuesday midway through a flight from Spain to Germany, apparently killing all 150 people on board.

The victims included two babies, two opera singers and 16 German high school students and their teachers returning from an exchange trip to Spain. It was the deadliest crash in France in decades.

The Airbus A320 operated by Germanwings, a budget subsidiary of Lufthansa, was less than an hour from landing in Duesseldorf on a flight from Barcelona when it unexpectedly went into a rapid descent, apparently in good weather.

The pilots sent out no distress call during the eight-minute descent and had lost radio contact with their control centre, France’s aviation authority said, deepening the mystery.

While investigators searched through debris from Flight 9525 on steep and desolate slopes, families across Europe reeled with shock and grief. Sobbing relatives at both airports were led away by airport workers and crisis counsellors.

“The site is a picture of horror. The grief of the families and friends is immeasurable,” German Foreign Minister Frank-Walter Steinmeier said after being flown over the crash scene. “We must now stand together. We are united in our great grief.”

Later in the day Germanwings had to cancel seven flights out of Dusseldorf because a number of crew members felt unfit to fly following news of the accident.

Lufthansa CEO Carsten Spohr said Tuesday evening he understood the crew members’ sentiments. “One must not forget that many of our Germanwings crews have known crew members who were onboard the crashed plane.”

The final 40 minutes of Flight 4U 9525

A search was launched as soon as it became obvious the plane had crashed but it took investigators hours to reach the site, led by mountain guides to a ravine near the town of Prads-Haute-Bléone in the southern French Alps, not far from the Italian border.

About 10 gendarmes were spending the night at the crash site to guard it, and search operations were to resume around dawn, said Lt. Col. Jean-Marc Meninchini of the regional police rescue service. Operations are expected to last a week.

Video shot from a helicopter and aired by BFM TV showed rescuers walking on rocky slopes on which plane parts are scattered. Photos showed white flecks of debris across a mountainside and larger airplane body sections with windows. A helicopter crew that landed briefly in the area saw no signs of life, French officials said.

“Everything is pulverized. The largest pieces of debris are the size of a small car. No one can access the site from the ground,” said Gilbert Sauvan, president of the general council, Alpes-de-Haute-Provence.

At least 10 coroners from the city of Marseilles were en route to the town of Seynes-les-alpes to receive the bodies of victims.

The last time a passenger jet crashed in France was the 2000 Concorde accident, which left 113 dead.

Among those missing in Tuesday’s crash are 16 high school students and two teachers from the German town of Haltern returning from an exchange trip to Spain.

They had spent a week in Llinars del Valles and were seen off at the town’s train station early Tuesday by their Spanish host families, said Pere Grive, the deputy mayor of the town of 9,000, about a 45-minute drive from Barcelona.

“We are completely shattered and the students are also devastated,” Grive told The Associated Press.

Other missing passengers included many Spaniards, two Australians and one person each from the Netherlands, Turkey and Denmark.

Contralto Maria Radner was returning to Germany with her husband and baby after performing in Wagner’s Siegfried, according to Barcelona’s Gran Teatre del Liceu. Bass baritone Oleg Bryjak had appeared in the same opera, according to the opera house in Duesseldorf.

The 24-year-old Airbus had experienced a technical problem with its nose landing-gear door on Monday morning, a Lufthansa spokeswoman confirmed. The problem involved a hatch that opens and closes when the nose landing gear is deployed and was solved through a routine repair, she said.

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In Germany, the airline’s chief said there was no sign that terrorism was involved in the crash, and German Chancellor Angela Merkel urged reporters not to speculate on the cause.

“We still don’t know much beyond the bare information on the flight, and there should be no speculation on the cause of the crash,” she said in Berlin. “All that will be investigated thoroughly.”

Lufthansa vice-president Heike Birlenbach told reporters in Barcelona that for now “we say it is an accident.”

Deadliest plane crashes in the past 10 years

Merkel, French President François Hollande and Spanish Prime Minister Mariano Rajoy were to visit the crash site Wednesday.

French Interior Minister Bernard Cazeneuve said a black box had been located and “will be immediately investigated.” He did not say whether it was the flight data recorder or the cockpit voice recorder.

The two devices — actually orange boxes designed to survive extreme heat and pressure — should provide investigators with a second-by-second timeline of the plane’s flight.

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 heard in the cockpit. The flight data recorder captures 25 hours’ worth of information on the position and condition of almost every major part in a plane.

The plane left Barcelona Airport at 10:01 a.m. local time and had reached its cruising height of 11,600 metres when it suddenly went into an eight-minute descent to just over 1,800 metres, Germanwings CEO Thomas Winkelmann told reporters in Cologne.

“We cannot say at the moment why our colleague went into the descent, and so quickly, and without previously consulting air traffic control,” said Germanwings’ director of flight operations, Stefan-Kenan Scheib.

At 10:30, the plane lost radio contact with the control centre but “never declared a distress alert,” said Eric Heraud of the French Civil Aviation Authority.

The plane crashed at an altitude of about 2,000 metres near the popular ski resort of Pra Loup.

“It was a deafening noise,” recalled Sandrine Boisse, president of the Pra Loup tourism office. “I thought it was an avalanche, although it sounded slightly different. It was short noise and lasted just a few seconds.”

The A320 enjoys a track record as one of the safest jets in the skies. For every million takeoffs, the A320 fleet has about 0.14 fatal accidents, according to a Boeing study that analyzed five decades of air disasters. That puts it on par with the Boeing 777 as one of the most reliable commercial planes.

“Canadian officials in Ottawa as well as in France, Germany and Spain are working with local authorities to determine whether any Canadians were onboard,” Caitlin Workman, a spokeswoman for Department of Foreign Affairs, Trade and Development in Ottawa, said in an email to the Star.

“Friends and relatives in Canada of Canadian citizens known to be travelling on this flight should contact DFATD’s 24/7 Emergency Watch and Response Centre by calling 613-996-8885 or 1 800 387-3124, or by sending an email to sos@international.gc.ca .”

With files from Jillian Kestler-D’Amours and Star wire services

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