- Search and recovery operation resumes after overnight lull
- More than 300 policemen and 380 firefighters mobilised
- Operation covers widely scattered debris field
- One flight recorder has been found but is damaged
Helicopter operations have resumed over mountainsides in the French Alps where a German airliner crashed, killing all 150 people on board.
Under overcast skies, with temperatures just above freezing, helicopters resumed flights on Wednesday over a widely scattered debris field.
The Airbus A320 operated by Germanwings, a budget subsidiary of Lufthansa, was less than an hour from landing in Dusseldorf on a flight from Barcelona on Tuesday when it unexpectedly went into a rapid descent.
One of the plane's "black box" recorders has been found, but it was unclear whether it was the flight data recorder or the cockpit voice recorder.
A source close to the inquiry on the disaster told AFP news agency the device was "damaged" and was being sent to Paris for investigation.
Investigators will continue searching for the second recorder on Wednesday.
More than 300 policemen and 380 firefighters have been mobilised.
A squad of 30 mountain rescue police resumed attempts to reach the crash site by helicopter at dawn on Wednesday, while a further 65 police were seeking access on foot.
Remote crash site
Five investigators spent the night at the crash site.
It would take "at least a week" to search the remote site, Lieutenant-Colonel Jean-Marc Menichini said, and "at least several days" to repatriate the bodies.
Video images from a government helicopter on Tuesday showed a desolate, snow-flecked landscape, with steep ravines covered in scree. Debris was strewn across the mountainside.
The plane was "totally destroyed", a local MP who flew over the site said, describing the scene as "horrendous".
A crisis cell has been set up in the area between Barcelonnette and Digne-les-Bains along with an emergency flight control centre to coordinate chopper flights to the crash site.
French President Francois Hollande, German Chancellor Angela Merkel and Mariano Rajoy, Spain's prime minister, were expected to reach the scene around 2pm local time (13:00 GMT).
The 144 passengers were mainly German and Spanish. At least three of victims were from the UK, British Foreign Secretary Philip Hammond said.
The high school in the small German town of Haltern attended by the 16 students on the plane was set to hold an event Wednesday to honour the victims.
Spain, meanwhile, has declared three days of mourning and was to hold a minute of silence across the country at noon on Wednesday.
Germanwings said the aircraft, travelling from Barcelona to Dusseldorf, lost height for eight minutes before crashing near the ski resort of Barcelonnette.
The rapid descent was "unexplained", Brice Robin, Marseilles prosecutor, said.
The pilots did not send out a distress call and had lost radio contact with their control centre, France's aviation authority said.
Weather did not appear to be a factor in the crash, with conditions calm at the time, French weather officials said.
Lufthansa, the parent company of Germanwings, said it was working on the assumption the crash was an "accident".
"Anything else would be speculation," Heike Birlenbach, Lufthansa vice president, said from Barcelona.
She said the 24-year-old Airbus aircraft had undergone its last routine check on Monday.
Thomas Winkelmann, Germanwings executive, said the pilot had "more than 10 years of experience" and about 6,000 flying hours on an Airbus jet under his belt.
It was the first fatal accident in the history of Germanwings, and the deadliest on the French mainland since 1974 when a Turkish Airlines jet crashed, killing 346 people.