"It is likely that there were some British nationals" on board the Germanwings flight that crashed today in the French Alps, with 150 people on board, Foreign Secretary Philip Hammond said.

A woman believed to be living in the north west of England and her baby son are said to be among those on board, according to officials.

There were apparently no survivors from the 144 passengers - including 16 schoolchildren and two teachers - and six crew after the plane went into an eight-minute descent before crashing near Digne.

Speaking this evening, the Mr Hammond said: "This is a tragic incident for those involved and their families, I send my deepest condolences to those who have lost family or friends.

"I don't want to speculate on numbers of British nationals involved until we have completed our checks on all the passenger information.

"However, based on the information available to us, it is sadly likely that there were some British nationals on board the flight. We are providing consular assistance and will give further help as more information becomes available.

"We are working closely with the French, German and Spanish authorities, and the airline, to establish the facts.

"The UK Air Accidents Investigation Branch, and UK disaster victim identification experts, are also standing by to offer assistance to the French authorities, if required."

The aircraft, operated by low-fare carrier Germanwings, was on its way from Barcelona to Dusseldorf when it crashed this morning on a mountainside near Meolans-Revels and the popular Pra Loup ski resort.

French authorities have tonight called off the complex search until the morning. The black box and flight data recorder - crucial in piecing together what happened - have both been found.

Also travelling on the plane with her baby was Marina Bandres, who came from Jaca in the Spanish Pyrenees and lived in Britain, Jaca mayor Victor Barrio said. Ms Bandres had been attending a funeral in the area for a relative.

Mr Barrio said he did not know if Ms Bandres' husband was on the flight with her and the boy, Julian, who was seven or eight months old.

Also among the passengers were two German opera singers - Dusseldorf-born contralto Maria Radner and bass baritone Oleg Bryjak, who was born in Kazakhstan.

The 16 pupils, from Joseph Konig school in Haltern am See in western Germany, were flying home after a week-long exchange with students at a school near Barcelona. The Spanish children in the exchange are still in Germany.

Haltern's mayor Bodo Klimpel said classes at Joseph Konig were suspended when news of the disaster came through, but that the school would be open as normal tomorrow when there would be a special event at morning assembly.

German chancellor Angela Merkel and various French ministers travelled to the crash site in a remote area.

Those on board the first helicopter to land near the site confirmed there were no survivors, with witnesses describing how the plane had disintegrated with no piece of wreckage bigger than a car.

Germanwings said the captain on board was experienced and had been with the airline and its parent company Lufthansa for more than 10 years and had clocked up 6,000 flying hours on this Airbus model.

Germanwings said the plane had a normal service at Dusseldorf yesterday and its last major check-up had been in summer 2013.

There was confusion about whether a distress signal was sent from the aircraft, with even Germanwings unsure.

A spokesman for the French civil aviation authority said the plane did not send a distress signal.

He said the plane lost radio contact at 10.30am local time but "never declared a distress alert itself".

He said it was the combination of loss of radio contact and the plane's descent that prompted the control service to declare a distress.

Prime Minister David Cameron and Deputy Prime Minister Nick Clegg said their thoughts were with the families of the passengers.

Mr Cameron's official spokesman said the Prime Minister had been informed of the crash and "would wish to express how his thoughts are very much with the families and friends of all of those aboard".

He added that the Foreign Office was making inquiries about whether any British nationals were on board, but had no information at this stage.

He said UK air accident investigators would offer any assistance requested by French or German authorities.

Spain's King Philip VI and Queen Letizia officially cancelled their state visit to France after they were told about the crash by French prime minister Manuel Valls.

A total of 67 Germans, many Spaniards, two Australians, and one person each from the Netherlands, Turkey, and Denmark were among the victims, according to their respective governments.

Spanish authorities were still trying to determine how many of their citizens were on board. The Mexican government said there were indications that one Mexican national was also among the victims.

French interior minister Bernard Cazeneuve tonight said the plane's black box had been found. Actually orange in colour, the black box comprises the cockpit voice recorder, giving investigators insight into pilots' conversations just before the crash, and the flight data recorder which shows how the workings of the plane were operating.

Brendan O'Neal, chairman of British airline pilots' association Balpa, said: "The UK pilot family stands with our German colleagues in this tragic moment.

"Our first thoughts are with the loved ones of the passengers, pilots and crew."

He went on: "It is too early to say what caused a reliable aircraft with a good safety record, modern technology and an experienced crew to crash."

Speaking at a media conference in Barcelona, a Lufthansa spokeswoman said the plane had been due to take off from Barcelona at 9.35am local time today but actually departed at 10.01am. It had been due to land in Dusseldorf at 11.55am local time.