SEYNE-LES-ALPES, France - The search for Germanwings Flight 9525, which crashed in the French Alps on Tuesday, took a grim turn when searchers arrived on the crash site to find everything "pulverized."
The Airbus A320 went down with 150 people on board in a snowy, remote section of the Alps, sounding like an avalanche as it scattered debris across the mountain.
AFP quoted a police officer in the town of Le Vernet, near the crash site, as saying shortly after the incident: "There is no need for any rescue operations, everyone is dead."
Aerial shots of the 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 one of the plane's two black boxes was recovered at the crash site. A spokesman for the ministry later said French investigators had already started to analyze it.
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.
After night fell, the search was called off for the night and helicopters were grounded. Lt. Col. Simon-Pierre Delannoy of the regional police rescue service said on BFM television that the conditions for the search had become too difficult.
A rescue official says about 10 police will spend the night at the site to guard the wreckage. The complex search operation was expected to resume Wednesday morning.
The pilots sent out no distress call and had lost radio contact with its control center, France's aviation authority said, deepening the mystery over the A320's mid-flight crash after an 8-minute surprise steep descent as it flew from Barcelona to Duesseldorf.
The crash left officials and families across Europe in shock. Sobbing, grieving relatives at both airports were led away by airport workers and crisis counselors.
"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," German Chancellor Angela Merkel told reporters in Berlin.
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.
Germanwings said Flight 9525 carried 144 passengers, including two babies, and six crew members. Officials believe 67 German nationals were on board, including 16 high school students on an exchange program from the German town of Haltern.
"It was a Spanish language exchange program and they were flying home after having what was probably the most wonderful time of their lives," local education minister Sylvia Loehrmann told Reuters.
Haltern Mayor Bodo Klimpel told reporters at a press conference "this is, of course, the worst thing you could imagine."
A Spanish opera house confirmed German contralto Maria Radner, along with her husband and baby, were among the victims. Earlier, an opera house in Duesseldorf said bass baritone Oleg Bryjak was also on board.
Barcelona's Gran Teatre del Liceu said Radner and Bryjak had performed in its production of Richard Wagner's "Siegfried."
The mayor of the small Spanish town of Jaca in the Pyrenees mountains says that a woman originally from the town died in the crash along with her baby boy.
Jaca Mayor Victor Barrio said Marina Bandres had been attending a funeral in Jaca for a relative and was taken to the Barcelona airport by her father.
Bandres lived in Britain. Barrio did not know if her husband was on the flight with her and the boy, Julian, who was seven or eight months old.
Spanish authorities were still trying to determine how many of their citizens were on board.
Business travelers included Carles Milla, the managing director for a small Spanish food machinery company, his office said, adding that he had been on his way to a food technology fair in Cologne. Two employees of Barcelona's trade fair organization were also on the flight.
Dutch officials said one citizen was killed. U.S. officials have told CBS News they have been unable to determine as yet whether there were any Americans on board.
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 said. The descent lasted eight minutes, he told reporters in Cologne.
Eric Heraud of the French Civil Aviation Authority said the plane lost radio contact at 10:30 a.m. Tuesday, but "never declared a distress alert itself." He said the combination of loss of radio contract with a control center and the plane's quick descent prompted the control service 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.
CBS News aviation and safety expert Capt. "Sully" Sullenberger, who famously piloted an Airbus A320 to safety in the Hudson River in New York City in 2009, said there are many reasons the plane could have descended, from instrument malfunctions to smoke in the cockpit.
While it will be impossible to know what happened until the black boxes are analyzed, Sullenberger said the long descent time "suggests that at least to some extent the pilots were able to control the airplane."
The plane crashed at an altitude of about 6,550 feet, at Meolans-Revels, near the popular ski resort of Pra Loup. The site is 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.
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 last underwent a routine check in Duesseldorf on Monday, and its last regular full check took place in the summer of 2013.
Germanwings is a lower-cost unit of Lufthansa, Germany's biggest airline, and serves mostly European destinations. It has been operating since 2002, part of traditional national carriers' response to competition from European budget carriers.
A Lufthansa vice president says the company is treating the crash as an accident for "the time being."
Heike Birlenbach told reporters in Barcelona that for now "we say it is an accident. There is nothing more we can say right now."
She also said that the plane, bound for Duesseldorf in Germany, took off from Barcelona 30 minutes late Tuesday but did not know what caused the delay.
The Germanwings logo, normally maroon and yellow, was blacked out on its Twitter feed.
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 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, 6 miles from the Val d'Allos ski resort, was being set up to take bodies from the crash.
Capt. Benoit Zeisser of the nearby Digne-le-Bains police said there were some clouds in the morning but the cloud ceiling was not low.
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 a live briefing 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 of the German plane with more than 140 people on board 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. The A320 is certified to fly up to 39,000 feet but it can begin to experience problems as low as 37,000 feet, depending on temperature and weight, including fuel, cargo and passengers.
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.