SEYNE-LES-ALPES, France - The ravine echoes with helicopter rotors, the scrape of metal on stone, the rumble of sliding scree as the remnants of Germanwings Flight 9525 dislodge from the mountainside.

The somber mission to recover the remains of 150 people killed when their plane slammed full speed into the Col de Mariaud is not a quiet one, and evidence can be gathered only when the mountains cooperate.

From 8:30 a.m. until 6 p.m., while the light is good, the helicopters ferry the crews into the ravine. It is too steep to land, so the 40 crewmembers are winched down singly or in pairs with packs bulging with clear plastic bags, red and yellow evidence tags, and the ropes they will use to keep each other from slipping when the black Alpine stone crumbles beneath their feet. Each investigator is linked to a local mountaineer, familiar with the terrain and with the skills to keep them safe.

Few pieces are larger than a car door. Most are smaller. And with each step the recovery workers make, crucial pieces of evidence slide inexorably downward. Some slip into a mountain brook fed by the snow that has only just begun melting in the French Alps.

"We have not found a single body intact," Col. Patrick Touron, one of France's leading forensic investigators, said Friday from Seyne-les-Alpes. "DNA will be the determining element that will lead to identification."

Between 400 and 600 biological elements have been retrieved and five scientists are in Seyne-les-Alpes to speed the process, he said. The families who arrived during the week provided objects such as toothbrushes, which belonged to the deceased, and some gave their own DNA samples to help cross-reference the forensic information found.

The moment a piece of human remains is found, forensic scientists have been taking a DNA sample immediately, from fears it could further decompose, and update the 150-person DNA database pool they are compiling on-site, Touron said. Jewelry and dental information are also key to the identification process, he said.

Touron noted the bodies would be returned to the families as soon as possible, but warned the process would be long.

Prosecutors say they believe German copilot Andreas Lubitz deliberately slammed the Germanwings aircraft into the.

A picture is emerging of Lubitz, 27, as a man haunted, whose ambition to fly brought him both pleasure and torment. Authorities have found doctors' sick notes stating he was unfit for work, including on the day of the crash.

On Saturday, Germany's Bild newspaper quoted an interview with a former girlfriend of Lubitz's who described a man who suffered from both vivid nightmares and delusions of grandeur.

"At night, he woke up and screamed: 'We're going down!' because he had nightmares," the former girlfriend told Bild. "He knew how to hide from other people what was really going on with him." She added that last year he had warned, "One day I will do something that will change the whole system, and then everybody will know my name and remember it."

Bild and the New York Times reported on Saturday that Lubitz was seeking treatment for vision problems, though it remained unclear whether the issue was real or perhaps psychosomatic. Such concerns could have led Lubitz to worry that he would permanently lose his medical certification to fly.

This article contains information from Bloomberg News.