Germanwings has said in a statement that its employees are "stunned" over the revelation that the plane was brought down deliberately.

"We would have never imagined that such a tragedy could happen in our company," it added.

The company described the incident as a "tragic individual case" and said that it still had complete confidence in its pilots.

The local government in Duesseldorf says the most recent regular security check on Andreas Lubitz, the Germanwings co-pilot, was conducted on 27 January and found nothing unusual, according to the Associated Press. The government says it also consulted the authorities in Bremen, where he went to flight school, and Rhineland-Palatinate state, where his hometown of Montabaur is located. The checks look for any criminal record or links to extremists.

James Reynolds
BBC News, Seyne-Les-Alpes

Marseille's prosecutor Brice Robin entered the room with no sign that he had an astonishing conclusion to reveal. He told reporters he had examined the voice recordings of the last 30 minutes of the flight. For the first 20 minutes, Mr Robin said, the captain and co-pilot spoke to each other normally - even cheerfully. Then the captain got up - apparently to use the toilet - and the cockpit door locked behind him. The co-pilot Andreas Lubitz was left alone in control of the plane. He soon pressed a button for the aircraft to descend. The prosecutor said he believed that this was a deliberate act.

Image source, AFP

The recordings picked up every detail of the co-pilot's actions - suggesting that he was conscious and alert. "We could hear him breathing. He breathed normally. He didn't utter a single word the minute the pilot left the cabin," Mr Robin said. The plane started to descend. The captain knocked on the cockpit door and used the intercom. But his co-pilot didn't respond. Trapped outside his own cockpit, the captain became increasingly desperate. "The alarms went off to alert the crew to the proximity of the ground and at that moment, we could hear a violent knocking on a door, someone was trying to force the door. It was a strong door, it was reinforced, in line with international norms, to protect against acts of terrorism." That meant there was no way in - and no way to stop the co-pilot. Andreas Lubitz calmly flew himself, his captain and their 148 crew and passengers straight into the mountainside.

Image source, Reuters

"I think that the victims did not realise what was happening until the last moment, the very last moment. Because in the recording, we could only hear the cries at the last moment, just before the impact with the ground." The prosecutor described their deaths as sudden and immediate. Brice Robin said he believed that Andreas Lubitz deliberately crashed the plane. If that turns out to be true, the final 10 minutes of the 28-year-old co-pilot's life were a sustained act of mass murder.

Twenty-eight-year-old co-pilot Andreas Lubitz is believed to have locked the doors of the cockpit and sent the Germanwings plane into descent with 150 people on board.

But who was he? Here is everything we know about Andreas Lubitz

A German foreign ministry spokesman says that 75 German nationals are now believed to have been killed in the crash, based on current information, according to Reuters. On Wednesday, Germanwings had put the number of German victims at 72.

A German state prosecutor has confirmed that police are searching properties in Duesseldorf and other locations for documents and evidence relating to the crash, Reuters news agency reports. Christoph Kumpa said it would take a while to assess the findings.

Andreas Lubitz lived with his parents in the town of Montabaur but also kept a flat in Duesseldorf.

Image source, AP

The US FBI has offered to help the French authorities with the air crash investigation. "We stand ready to fulfil any requests for information," FBI spokesman Paul Bresson told the Associated Press.

James Longman
BBC News

tweets, external: "A map circling #GermanWingsCrash exclusion zone from helicopter high over the #Alps @BBCNews"

Image source, James Longman

Matthias Gebauer
Der Spiegel magazine

tweets:, external "Looking for a motive for the deadly descent: Police begin search warrant at #4U9525 co-driver Andreas L. Montabaur"

Our correspondent Jenny Hill has been speaking to residents near the family home of Andreas Lubitz in Montabaur, shown below.

She reports: "'It's just horrible,' one neighbour told me as she held her little boy. She didn't know the family well at all. But she worries now that Montabaur will always be remembered for this.

"A little while ago two people strode up to the front door escorted by police officers. A woman, maybe in her 30s, carrying a notebook and a slightly older man were let into the house and the heavy brown door slammed shut again."

Image source, Reuters

Families of some of the victims have now arrived in Seyne-les-Alpes, near the crash site. The local bishop is shown here preparing to greet and support those relatives.

Image source, AFP/Getty

BBC correspondent Jenny Hill is in Montabaur, where Germanwings co-pilot Andreas Lubitz is thought to have lived.

She says: "It's an unremarkable house in a small quiet housing estate. But this is where Andreas Lubitz is believed to have lived with his parents - and the house with grey walls and dormer windows is now the focus of the world's attention as investigators try to establish why he appears to have deliberately crashed the plane."

She said today's news was "an additional strain on the families and in this hour full of suffering, these days full of suffering, our thoughts are especially with them".

Mrs Merkel said that Germany would do all it could to support the investigation into the crash.

German Chancellor Angela Merkel said she has been deeply shocked by the latest developments. "It is difficult to measure the suffering that this catastrophe has brought to so many families," she tells a news conference in Berlin. "Today, we now have received news that this tragedy has been given a new, immeasurably incomprehensible dimension."

How are cockpit doors locked? BBC Magazine takes a look at how aircraft security systems work here.

A 30-minute recording obtained from the cockpit voice recorder has provided the clearest indication yet as to what might have happened on board. Take a look at our analysis of the flight's final half hour.

A coach transporting relatives of some of the victims has arrived in Seyne-les-Alpes, near the crash site in the French Alps.

Image source, Reuters

Lufthansa CEO Carsten Spohr has described the entry mechanism of the cockpit door.

"There is another code you can enter at the door which will lead to a bell ringing and if nobody reacts, the door will open automatically and allow entry," he said.

But he added that this can be blocked from the cockpit by pushing a switch that will lock the door for five minutes.

"Either the captain didn't enter the code correctly - which we find unlikely because everybody involved knows this code by heart - or the colleague had entered the code and the co-pilot prevented the door from opening by pushing the lock switch," said Mr Spohr.

Low-cost airline Norwegian Air Shuttle will now require two people to be in the cockpit at all times for safety reasons. "When one person leaves the cockpit, two people will now have to be there," its director of operations is quoted as saying by AFP news agency.

French prosecutors say the pilot of the Germanwings plane that crashed was locked out of the cockpit by his co-pilot, who then "voluntarily" sent the plane into a descent.