An Airbus plane that crashed in the French Alps, killing everyone on board, is believed to have been carrying 16 schoolchildren and two babies.
The Germanwings A320 had 144 passengers and six crew on board.
Flight 4U 9525 was flying from Barcelona to Dusseldorf when it crashed at an altitude of 6,500ft in the mountainous zone of Meolans-Revels, near Digne.
Among the passengers were 67 Germans and 45 Spanish citizens.
German newspaper Bild is reporting that 16 teenagers and two teachers from Haltern, in western Germany, are among the dead.
France's Transport Ministry confirmed on Tuesday afternoon there were no survivors.
French prime minister Manuel Valls said a helicopter has managed to land near the crash site.
Gilbert Sauvan, an official with the local council, told Les Echos newspaper: "The plane is disintegrated.
"The largest debris is the size of a car."
Interior Ministry spokesman Pierre-Henry Brandet said he expects "an extremely long and extremely difficult" search and rescue operation because the area is so remote.
It is surrounded by mountains and there are few clear trails to the snow-covered area.
The plane sent out a distress signal at 10.45am local time (9.45am GMT).
The boss of Germanwings said the plane went into a long descent before it crashed.
Germanwings CEO Thomas Winkelmann said the plane began descending again shortly after it reached its cruising height following take-off from Barcelona Airport.
The descent lasted eight minutes, he told reporters in Cologne. Radar and air traffic control contact broke off at 10.53am.
He said the pilot had more than 10 years' experience working for Germanwings and its parent airline Lufthansa. Airbus said the A320 was delivered to Lufthansa in 1991.
Germanwings said the passenger manifest included two babies. Officials believe there were 67 German nationals on board.
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 said.
"The noise I heard was long - like eight seconds - as if the plane was going more slowly than a military plane. There was another long noise after about 30 seconds."
Mr Polizzi said the plane crashed about 3 to 11 miles (5 to 8km) 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, six miles (10 kilometres) from the Val d'Allos ski resort, was being set up to take bodies or survivors from the crash, according to Sandrine Julien of the town hall.
There was no obvious weather reason why the plane went down. Captain Benoit Zeisser of the nearby Digne-le-Bains police said there were some clouds but the cloud ceiling was not low.
In addition, the safest part of a flight is when the plane is at cruising elevation. Just 10% of fatal accidents occur at that point, according to a safety analysis by Boeing. In contrast, take-off and the initial climb accounts for 14% of crashes and final approach and landing accounts for 47%.
Germanwings official Oliver Wagner told German television that Germanwings flight 9525 carried 144 passengers and six crew members. He did not give a breakdown of nationalities on board.
Germanwings is a lower-cost unit of Lufthansa, Germany's biggest airline.
It has been operating since 2002, part of traditional national carriers' response from rising European budget carriers. It serves mainly European destinations.
The Germanwings logo, normally maroon and yellow, was blacked out on its Twitter feed.
Family members arriving at Dusseldorf airport were taken from the main terminal to a nearby building, which airport employees partially covered with sheets for privacy.
At Barcelona airport, police escorted several crying women to a part of the airport away from the media. One woman held a jacket over the head of another woman, who was sobbing.
In a live briefing, the French President Francois Hollande said it was likely that a number of the victims were German. "It's a tragedy on our soil," he said.
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.
German chancellor Angela Merkel spoke to both Mr Hollande and Spanish prime minister Mariano Rajoy about the crash, immediately cancelling all other appointments.
At a briefing in Berlin, Ms Merkel told reporters she would travel to the crash site region tomorrow, and that Germany's foreign and transport ministers were already en route.
She said her thoughts were "with those people who so suddenly lost their lives, among them many compatriots".
"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," Ms Merkel said.
She reminded everyone that the cause was not known.
"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. "All that will be investigated thoroughly."
The A320 plane is a workhorse of modern aviation. Similar to the Boeing 737, the single-aisle, twin-engine jet is used to connect cities between one and five hours apart. Worldwide, 3,606 A320s are in operation, according to Airbus.
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.
The A320 family also has a good safety record, with just 0.14 fatal accidents per million take-offs, according to a Boeing safety analysis.
The German Federal Bureau of Aircraft Accident Investigation was sending three people to France to join the investigation.
French interior minister Bernard Cazeneuve, the country's top security official, and the German ambassador in Paris were among those heading to the crash site.
In Madrid, Mr Rajoy suspended his agenda to preside over an emergency government meeting about the crash.
"Like everyone, I lament this incredibly sad and dramatic accident," Mr Rajoy said.
Antonio San Jose, spokesman for the Spanish airport authority AENA, said his agency was working with Germanwings to reach out to relatives of the victims.
Spain's king and queen, in Paris today, cancelled their previously planned state visit and offered their condolences to all who lost a loved one in the crash.