However, they denied German media reports body parts of co-pilot Andreas Lubitz had been identified.
The cockpit voice recorder suggested he crashed the plane deliberately.
A transcript leaked to German media revealed the frenzied final minutes, with the pilot, locked out of the cockpit, shouting "open the damn door!"
Recovery teams have so far only reached the mountainside on foot or by helicopter to continue the search for human remains as well as parts of the aircraft, including the flight data recorder which is still missing.
Marseille prosecutor Brice Robin said an access road was being built to the remote site.
Mr Robin said work on the road, which would give all-terrain vehicles access to the area, could be completed by Monday evening.
The German newspaper Bild published a transcript of the final minutes of the flight as caught on the cockpit voice recorder. It has not been independently verified.
It shows the captain, who has been named in media as Patrick Sondenheimer, telling Lubitz he was not able to go to the toilet before take off, to which the co-pilot replies he can go at any time.
The captain says "you can take over".
Lubitz, 27, then appears to refuse to let the captain back into the cockpit.
The captain can be heard banging on the door and screaming: "For God's sake, open the door!"
The captain tries to break the door down with an axe. Passengers are then heard screaming as the captain begs again to be let in.
Investigators think there is the sound of the plane's wing hitting a mountaintop before final screams.
Meanwhile, there have been calls for a full investigation to be completed before any further conclusions are revealed.
The German Airline Pilots Association pointed out that the flight data recorder was still missing and that the reasons that led to the crash could only be determined once all data had been examined.
The European Cockpit Association said the release of voice recorder data was a "serious breach" of globally accepted rules. It said many questions remained unanswered.
The suggestion that the co-pilot's action was deliberate led to speculation about his mental health, especially when investigators found anti-depressants at his house along with evidence of treatment by various doctors, including a torn-up sick note for the day he flew the plane.
Reports about problems with his eyesight - possibly a detached retina - first raised in the New York Times, were also reflected in the German papers.
But no full picture has emerged of what initially caused Lubitz to seek medical help and whether reports that he was stressed are linked to a prospect of impaired vision and its potential impact on his ambition of becoming a long-haul pilot for Germany's main carrier Lufthansa.
Lufthansa, which fully owns Germanwings, says his training was once interrupted but only resumed after his suitability was fully re-established.
Lubitz's ex-girlfriend has said he vowed last year: "One day I'm going to do something that will change the whole system, and everyone will know my name and remember."
Family members continue to travel to the site of the crash.
Ippei Yamanaka, co-worker of victim Junichi Sato, told AP: "His wife says she still she cannot believe what has happened, saying that it almost feels like her husband is away on his business trip and that it still feels like he is going to return soon."
An official memorial service for those onboard flight 4U9525 from Barcelona to Duesseldorf will be held on 17 April in Germany's most famous church - Cologne Cathedral - in the presence of President Joachim Gauck and Chancellor Angela Merkel.
Meanwhile, the pastor of the Lutheran church in Andreas Lubitz's hometown, Michael Dietrich, told Associated Press the church was standing behind the family. He said there had been no direct contact with the family but he believed they were receiving good help.
French prosecutors are also yet to question the Lubitz family.
Unanswered questions
What drives people to murder-suicide?
Who was Andreas Lubitz?
Five days after Germanwings flight 4U 9525 crashed in the French Alps killing all 150 on board, investigators say they have isolated DNA of 78 victims.