SEYNE-LES-ALPES, France (AP) — A Germanwings jet carrying 150 people from Barcelona to Duesseldorf slammed into a remote section of the French Alps on Tuesday, sounding like an avalanche as it scattered pulverized debris across a rocky mountain and down its steep ravines. All aboard were assumed killed.

The pilots sent out no distress call and had lost radio contact with their control center, France’s aviation authority said, deepening the mystery over the A320’s mid-flight crash after a surprise 8-minute descent.

The crash left officials and families across Europe reeling in shock. Sobbing, grieving relatives at both airports were led away by airport workers and crisis counselors. One German town was rent with sorrow after losing 16 high school students coming back from an exchange program in Spain.

“This is pretty much the worst thing you can imagine,” a visibly rattled Haltern Mayor Bodo Klimpel said at a hastily called press conference.

As helicopters were deployed to reach the crash site, 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.”

In Washington, the White House said American officials were in contact with their French, Spanish and German counterparts.

“There is no indication of a nexus to terrorism at this time,” said U.S. National Security Council spokeswoman Bernadette Meehan.

Photos of the crash site showed scattered black flecks across a mountain and several larger airplane body sections with windows, five in one chunk and four in another. French officials said a helicopter crew that landed briefly in the area saw no signs of life.

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

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

Germanwings is low-cost carrier owned by Lufthansa, Germany’s biggest airline, and serves mostly European destinations. Tuesday’s crash was its first involving passenger deaths since it began operating in 2002. The Germanwings logo, normally maroon and yellow, was blacked out on its Twitter feed.

Germanwings said Flight 9525 carried 144 passengers, including two babies, and six crew members. Officials believe 67 Germans were on board, including 16 high school students from Haltern, and, according to the opera house in Duesseldorf, bass baritone Oleg Bryjak. Dutch officials said one citizen was killed.

The plane left Barcelona Airport at 10:01 a.m., then began descending again shortly after reaching its cruising height of 38,000 feet, Germanwings CEO Thomas Winkelmann told reporters in Cologne. The descent lasted eight minutes.

Eric Heraud of the French Civil Aviation Authority said the Germanwings plane lost radio contact with a control center at 10:30 a.m. Tuesday, but “never declared a distress alert itself.” He said the combination of loss of radio contract and the plane’s quick descent prompted the control center to declare a distress situation.

“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.

The plane crashed at an altitude of about 2,000 meters (6,550 feet) at Meolans-Revels, near the popular ski resort of Pra Loup. The site is 700 kilometers (430 miles) south-southeast of Paris.

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

Interior Ministry spokesman Pierre-Henry Brandet told BFM television he expected “an extremely long and extremely difficult” search-and-rescue operation because of the area’s remoteness. The weather in the area deteriorated Tuesday afternoon, with a chilly rain falling.

Winkelmann said the pilot, whom he did not name, had more than 10 years’ experience working for Germanwings and its parent airline Lufthansa.

The aircraft was delivered to Lufthansa in 1991, had approximately 58,300 flight hours in some 46,700 flights, Airbus said. The plane underwent a routine check in Duesseldorf on Monday, and its last regular full check took place in the summer of 2013.

Winkelmann said teams from Airbus, Germanwings, Lufthansa and Lufthansa’s technical division had arrived in France and were on their way to the crash site.

The owner of a campground near the crash site, Pierre Polizzi, said he heard the plane making curious noises shortly before it crashed.

“At 11.30, I heard a series of loud noises in the air. There are often fighter jets flying over, so I thought it sounded just like that. I looked outside, but I couldn’t see any fighter planes,” he told the AP. “The noise I heard was long — like 8 seconds — as if the plane was going more slowly than a military plane. There was another long noise after about 30 seconds.”

Polizzi said the plane crashed about 5-to-8 kilometers (3-to-11 miles) from his place, which is closed for the season.

“It’s going to be very difficult to get there. The mountain is snowy and very hostile,” he said.

The municipal sports hall of Seyne-les-Alpes, 10 kilometers (6 miles) from the Val d’Allos ski resort, was being set up to take bodies from the crash.

The safest part of a flight is normally when the plane is at cruising elevation. Just 10 percent of fatal accidents occur at that point, according to a safety analysis by Boeing. In contrast, takeoff and the initial climb accounts for 14 percent of crashes and final approach and landing accounts for 47 percent.

In Paris, French President Francois Hollande called the crash “a tragedy on our soil.”

The last time a passenger jet crashed in France was the 2000 Concorde accident, which left 113 dead — 109 in the plane and four on the ground.

Merkel spoke with both Hollande and Spanish Prime Minister Mariano Rajoy about the crash, immediately cancelling all other appointments.

“The crash … is a shock that plunges us in Germany, the French and the Spanish into deep sorrow,” said Merkel, who planned to travel to the region Wednesday.

The A320 plane is a workhorse of modern aviation. The single-aisle, twin-engine jet is used to connect cities between one and five hours apart. It is certified to fly up to 39,000 feet but it can begin to experience problems as low as 37,000 feet.

Worldwide, 3,606 A320s are in operation, according to Airbus.

The A320 family also has a good safety record, with just 0.14 fatal accidents per million takeoffs, according to a Boeing safety analysis.

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Hinnant contributed from Paris. Thomas Adamson and Elaine Ganley in Paris, David McHugh in Frankfurt, Geir Moulson and David Rising in Berlin, Frank Augstein in Duesseldorf, Al Clendenning in Madrid, Joe Wilson in Barcelona, Kirsten Grieshaber from Haltern, Germany, and AP Airlines writer Scott Mayerowitz in New York contributed.