Searches have been called off for the night at the site of a plane crash in the French Alps.

150 people were on board the Germanwings flight from Barcelona to Dusseldorf, but rescuers say there's likely to be no survivors.

16 children and two teachers on the plane were from the same school in Haltern in north-west Germany.

The black box belonging to the plane has been found - while the cause of the crash remains a mystery.

French Interior Minister Bernard Cazeneuve says a black box has been located at the site where the plane travelling between Barcelona to Dusseldorf.

Weather has already been ruled out by experts as a cause, and US officials say terrorism is also unlikely.

Investigators hope the black box will provide clues about the cause of the crash and will look at possibilities, including engine failure.

Aviation sources suggests that the speed of the plane shortly prior to the crash - about 350mph (300 knots) - might suggest engine failure as a cause.

This is because 350mph is the speed a pilot would aim to reach before trying to "relight" the engines after a double engine failure, sources told Sky News.

Flight 4U 9525, which left the Spanish city at 10.01am (local time) had started descending one minute after reaching its cruising height.

It then plummeted from 38,000ft to 6,000ft in less than eight minutes before it crashed.

French aviation authorities said the plane did not issue a distress call and lost radio contact with air traffic controllers at 10.30am.

At a press conference this afternoon, a Lufthansa spokeswoman said that the plane departed nearly 30 minutes late - and the reason for this was unclear.

The plane had undergone routine technical checks yesterday, the spokeswoman added.

"We do not want to speculate about what happened aboard that flight - we do not have the information at the moment," the spokeswoman added.

Conditions in the region of the crash were not out of the ordinary, with no significant storms in the area.

Dr Rob Thompson, a meteorologist at the University of Reading, said: "The weather conditions in the area of southern France where the crash is reported to have occurred look like nothing out of the ordinary for this time of year.

"Wind speeds on the ground showed breezy conditions, although this does not indicate the conditions higher up in the atmosphere.

"Available satellite imagery shows there were not any significant storm systems locally.

"Data from lightning detectors show the nearest electrical storms were occurring in Sardinia, some 186 miles off the south coast of France, which would be much too far away to cause any issues to air traffic."

Airbus said a team of its technical advisers has been sent to the scene to help the French air accident investigators.

They are trying to establish what triggered the plane's eight-minute descent before crashing.

The A320 aircraft is one of the most popular passenger planes in the world, used by most airlines.

Known for its efficiency and advanced technology, more than 11,000 orders for planes from the A320 family have been made since its launch in 1987.

Aviation safety expert Alex Macheras told Sky News: "The A320 is used almost by every airline that has short-haul operations, from British Airways to easyJet and American airlines.

"Every airline which operates the short flights goes for the A320 because they are a very efficient aircraft, modern and up-to-date and they have the latest technology on the flight deck which makes flying them a treat."

Captain Mike Vivian added: "It is a very good plane. They are operating all over the world and they are intrinsically a short-haul aircraft and have a very good safety record."

The A320 aircraft family is made up of narrow-bodied short to medium range twin engine jets. The first flight took place on 22 February 1987.

There have been 60 incidents known as "aviation occurrences" since the aircraft family was introduced, resulting in 789 fatalities up to 23 March.

One of the best-known incidents involving an A320 aircraft was the so-called Miracle on the Hudson in which a plane crash-landed in New York's Hudson River. All 155 people on board survived.

The AirAsia plane which crashed into the Java Sea in December was also an Airbus A320.

The Airbus A320 which crashed in France on Tuesday is operated by Germanwings, a budget airline which is wholly owned by Lufthansa. The aircraft was manufactured in 1991.

Germanwings has 81 aircraft operating out of Cologne, Bonn, Hamburg, Berlin and Dusseldorf.