A rescue helicopter has landed at the site of the Germanwings air disaster in the French Alps to find the plane "disintegrated" and no survivors.

The Airbus A320 with 150 people on board came down into a mountainous region, at an altitude of around 6,500ft, between Barcelonnette and Digne.

After taking off at 9:55am (8:55am Irish time), a distress signal was issued for flight 4U 9525 at 10:47am (9:47am Irish time) after it found itself in an "abnormal situation" on its route from Barcelona to Dusseldorf.

The French Prime Minister Manuel Valls said a helicopter had managed to land near the crash site but found no survivors.

Gilbert Sauvan, of the local council, told Les Echos newspaper: "The plane is disintegrated. The largest debris is the size of a car."

A Germanwings plane waits at the airport in Dusseldorf, Germany | Image: Martin Meissner / Associated Press

In a statement, Lufthansa said:"We must confirm to our deepest regret that Germanwings Flight 4U 9525 from Barcelona to Düsseldorf has suffered an accident over the French Alps."

"The flight was being operated with an Airbus A320 aircraft, and was carrying 144 passengers and six crew members."

"Lufthansa and Germanwings have established a telephone hotline. The toll-free 0800 11 33 55 77 number is available to all the families of the passengers involved for care and assistance."

"Everyone at Germanwings and Lufthansa is deeply shocked and saddened by these events Our thoughts and prayers are with the families and friends of the passengers and crew members"

It adds that the Lufthansa CEO Carsten Spohr and representatives of the German government are on their way to France.

"A tragedy on our soil"

French President Francois Hollande said: "It's a tragedy on our soil."

Spain's Deputy Prime Minister, Soraya Sáenz de Santamaría, said 45 of those on board are thought to be Spanish. Germanwings said there were 67 Germans on board.

German Chancellor Angela Merkel was "deeply shaken" by news of the crash, her spokesman said.

French Interior Ministry spokesman Pierre-Henry Brandet said debris from the crash had been found at an altitude of 2,000 metres.

He added that he expected "an extremely long and extremely difficult" search and rescue operation because of the area's remoteness.

Emergency workers were not expected to reach the scene for several hours.

Eric Ciotti, the head of the regional council, said search-and-rescue teams were on the way to the crash site at Meolans-Revels.

Flight-tracking data indicated the aircraft plummeted from 40,000ft to 6,200ft in less than eight minutes before it crashed.

French aviation authorities said that the plane, operated by Lufthansa's budget airline, did not issue a distress call and that air traffic controllers had raised the alarm.

Aviation expert Gerry Byrne told Newstalk Lunchtime the plane appeared to take a sharp dive.

Babies and schoolchildren on board

A total of 144 passengers, two pilots and four cabin crew were on board the 24-year-old plane. A spokeswoman for the German town of Haltern said there was reason to believe the passengers included 16 pupils and two teachers from one school.

Media reports in Germany said earlier that the schoolchildren and teachers were from Joseph-Koenig Gymnasium high school in the town in North Rhine Westphalia state.

The headmaster of the school has sent students home, and parents have already gathered at Dusseldorf Airport where the Airbus A320 was scheduled to arrive, Halterner Zeitung reported.

At a press conference, airline Germanwings said there were two babies on the flight, which had left Barcelona bound for the city.

Germanwings chief executive Thomas Winkelmann told a news conference the pilot had more than 10 years experience, including more than 6,000 flight hours on A320s.

He said the firm would do everything possible to establish the cause of the crash.

The owner of a campground near the crash site, Pierre Polizzi, said he heard the aircraft making strange noises just before it crashed.

"I heard a series of loud noises in the air," he said.

A family of people involved in a crashed plane arrives at the Barcelona airport in Spain | Image: Emilio Morenatti / Associated Press

"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. The noise I heard was long - like eight seconds - as if the plane was going more slowly than a military plane speed. There was another long noise after about 30 seconds."

Weather conditions were calm at the time the plane came down and Mr Valls said the causes of the crash were not yet known.

Reports suggest debris at the crash site is not scattered, indicating there had been no mid-air explosion.

German foreign minister Frank-Walter Steinmeier said in a tweet: "Our thoughts are with those who have to go through the worry that their relatives may be among the victims."

Spain correspondent with The Times, Graham Keeley, is in Barcelona and says the sense of shock is palpable.

Peter Allen is a journalist in Paris. He told Newstalk Lunchtime the crash site is a very remote location.

The apparent route and crash site of the plane | Image: Flightradar

The Department of Foreign Affairs has set up a phone number for those concerned about relatives and friends to call.

DFAT is liaising with authorities through our Embassies in Paris, Madrid and Berlin. If you have concerns, please call us on 01-408 2527.

— DFATravel (@dfatravel) March 24, 2015