Updated | No survivors feared in Germanwings A320 crash in French Alps

A Germanwings Airbus A320 plane carrying at least 150 people crashed Tuesday, in a mountainous area of southeastern France.

Those aboard flight 4U 9525, flying from Barcelona, Spain, to Dusseldorf, Germany – 144 passengers and six crew members – are believed to be dead.

Although the passenger list is not yet official, 45 of the passengers are believed to be Spaniards, 67 are thought to be German nationals.  Reports said that a group of 16 German teenagers returning from an exchange trip to Spain were booked on the flight, but school officials could not confirm whether the students had boarded the aircraft.

A “black box” flight recorder was found at the site of the plane crash, as rescue teams reached the remote Alpine location of the disaster on Tuesday. There was no immediate clue as to the cause of the crash, which happened in calm weather conditions.

Aviation experts were puzzled as to why the crew reportedly failed to raise the alarm as the plane dropped from the sky and changed trajectory to avoid smashing into the mountain.

INFO: We have recently become aware of media reports speculating on an incident though we still do not have any own confirmed information...

— Germanwings (@germanwings) March 24, 2015

The Maltese parliament on Tuesday afternoon paid a minute of silence in solidarity with the victims of the plane crash and their relatives. Prime Minister Joseph Muscat informed parliament that, so far, information coming in through the Maltese embassy in Spain showed that there were no Maltese nationals on board the plane.

The low-cost Germanwings carrier is a Lufthansa subsidiary.

German Chancellor Angela Merkel has expressed deep shock at the tragedy, adding that she was planning to travel to the site of the crash.

Flight path of crashed Germanwings #A320 shows steep descent #4U9525 pic.twitter.com/Cu8AFAnxC1

— Karel Souffriau (@karelxwb) March 24, 2015

One witness, Sebastien Giroux, said he saw the plane flying very low in the southern Alps near Digne-les-Bains, near where it crashed. “There was no smoke or particular sound or sign of anything wrong, but at the altitude it was flying it was clearly not going to make it over the mountains,” he told BFM-TV. “I didn’t see anything wrong with the plane, but it was too low.”

A rescue helicopter managed to reach the site in a remote mountainous region.

Je veux exprimer aux familles des victimes de cet accident aérien toute ma solidarité. C'est un deuil, une tragédie.

— François Hollande (@fhollande) March 24, 2015

Local council official Gilbert Sauvan told Les Echos newspaper that the crash was so extreme that the plane had “disintegrated”, adding that “the largest piece of debris is the size of a car.”

Early Tuesday morning, French President Francois Hollande said no survivors were expected. The plane crashed near Digne les Bains, in the Alpes de Haute Provence region.

“The conditions of the accident are not yet clear but lead us to believe there will be no survivors,” Hollande said.

“We are trying to understand all the elements that cause this, and we will give them to all relevant officials, Spanish and German... it is a great loss that we have to bear, that has occurred on our soil,” the French President said.

The French aviation regulatory authority (DGAC) said the aircraft did not issue a distress call, as initially reported, but that its sudden drop in altitude had led air traffic controllers to implement the “distress phase”. This is the third and most serious of three alerts used to help identify and coordinate rescue efforts when a plane is thought to be in difficulty.

Germanwings managing director Thomas Winkelmann told reporters that the plane began descending one minute after reaching its cruising height and that it continued to lose altitude for eight minutes.

Winkelmann added that the aircraft had lost contact with French air traffic controllers at around 10:53am at an altitude of around 6,000 feet, but it is yet unclear whether the plane had sent a distress signal prior to the crash.

The crash occurred in mountainous terrain near the village Prads-Haute-Bléone, French police Capt. Benoit Zeisser said. Because of the terrain, it will be a difficult site for rescuers to access, Zeisser said. A police helicopter is in the area, he said.

Hundreds of gendarmes, firefighters and emergency search and rescue teams, as well as 10 helicopters and a military aircraft, were dispatched to the crash site to search for survivors. The crash zone is isolated, extremely difficult to reach and completely inaccessible to vehicles.

The twin-engine Airbus A320, which entered service in 1988, is generally considered among the most reliable aircraft and it is widely used by various airlines, including Air Malta, Air France and British Airways among others.

Crashes mid-flight are rare, as most happen near take-off or landing.