The relatives of the Germanwings victims may have to wait months for their loved ones to be identified, with no guarantees they will all be found - Germany's Bild newspaper has reported.

The head of the Criminal Research Institute at France's National Gendarmerie said it would take forensic teams between two and four months to complete the DNA identification process, according to Bild.

Even then, "we cannot promise that we will be able to identify all of the victims," Colonel Francois Daoust said.

The violence with which the plane crashed into the mountainside in the French Alps last week has severely hampered the identification of the remains of the 150 people on board.

Recovery teams scouring the crash site have said not a single body has been found intact.

Some 78 different DNA profiles have been isolated so far from around 400 body parts, although none have been directly linked to the victims.

Family members have been asked to provide forensic teams with DNA samples to help in the identification.

Investigators are currently working on the theory that the co-pilot, Andreas Lubitz (27), deliberately crashed the plane.

The voice recorder suggested he locked the pilot out of the cockpit and intentionally put the Airbus A320 into a descent.

Treated for suicidal tendencies

German prosecutors revealed on Monday that Mr Lubitz had been treated in the past for suicidal tendencies, although no evidence has been found to prove he felt suicidal at the time of the crash.

Christoph Kumpa, a spokesman for Dusseldorf prosecutor's office, said he was known to have paid several visits to doctors in the days and months before and nothing of this nature was found to have been documented.

He said: "There still is no evidence that the co-pilot told before that he'll do what we have to assume was done and we haven't found a letter or anything like that that contains a confession."

"Added to this, we have not found anything in the surrounding be it personal, or his family, or his professional surrounding, that is giving us any hints that enable us to say anything about his motivation."

Mr Lubitz had been given a sick note on the day of the crash, but the note was never submitted to Germanwings.

It has been reported he had also been receiving treatment for an unspecific vision problem which could have affected his ability to fly, although Mr Kumpa said nothing had been found to verify those claims.

Investigators have so far been unable to find the aircraft's second black box, which would provide technical flight data of its final moments.

French investigators have been working on the construction of the road to improve access to the crash site.