Berlin (AFP) - The captain of a passenger jet that investigators believe was deliberately crashed into the French Alps, killing all 150 aboard, shouted at the co-pilot to "open the damn door" as he desperately tried to get back into the locked cockpit, a German newspaper reported Sunday.
Forensic teams meanwhile announced that they had isolated 78 distinct DNA strands from body parts at the mountain crash site with investigators describing the difficulty of the search as "unprecedented" due to the arduous terrain.
French officials say the plane's black box voice recorder indicates that Andreas Lubitz, 27, locked the captain out of the cockpit of the Germanwings jet and steered Flight 4U 9525 into a mountainside.
They believe that the more senior pilot, identified by Germany's Bild newspaper as Patrick S., tried desperately to reopen the door during the Barcelona to Duesseldorf flight's eight-minute descent after he left to use the toilet.
The mass-circulation paper's Sunday edition reported that data from the cockpit recorder showed the captain shouted: "For God's sake, open the door", as passengers' screams could be heard in the background.
It said "loud metallic blows" against the cockpit door could then be heard, before another warning alarm went off and then the pilot is heard to scream to a silent Lubitz in the cockpit "open the damn door".
Investigators in the Alps said the violence of the impact and the remote location was severely hampering the search for both body parts and the second "black box".
"We haven't found a single body intact," said Patrick Touron, deputy director of the police's criminal research institute.
"We have slopes of 40 to 60 degrees, falling rocks, and ground that tends to crumble," said Touron. "Some things have to be done by abseiling."
As investigators seek to build up a picture of Lubitz and any possible motives, media reports have emerged that he suffered from eye problems, adding to earlier reports he was severely depressed.
German prosecutors believe Lubitz hid an illness from his airline but have not specified the ailment, and said he had apparently been written off sick on the day the Airbus crashed.
- 'Sight problem' -
The Sunday edition of Germany's Bild tabloid and the New York Times, which cited two officials with knowledge of the investigation, said Lubitz had sought treatment for problems with his sight.
It is thought to be a retinal detachment, the German weekly said.
It also reported that Lubitz's girlfriend with whom he lived in the western city of Duesseldorf was believed to be pregnant.
It gave no sources but said the teacher, who taught maths and English, had told pupils a few weeks ago she was expecting a baby.
Bild's Saturday edition had published an interview with a flight attendant who it said had had a relationship last year with Lubitz and recalled him saying: "One day I'm going to do something that will change the whole system, and everyone will know my name and remember."
If Lubitz did deliberately crash the plane, it was "because he understood that because of his health problems, his big dream of a job at Lufthansa, of a job as captain and as a long-haul pilot was practically impossible", the woman told Bild.
German prosecutors revealed Friday that searches of Lubitz's homes netted "medical documents that suggest an existing illness and appropriate medical treatment", including "torn-up and current sick leave notes, among them one covering the day of the crash".
Police have found a number "of medicines for the treatment of psychological illness" during a search at his Duesseldorf home, Welt am Sonntag newspaper said.
It added that the Germanwings co-pilot was suffering from being overstressed and was severely depressive, according to personal notes found.
- Search for second black box -
French police investigator Jean-Pierre Michel told AFP Saturday that Lubitz's personality was a "serious lead" in the inquiry but not the only one.
The investigation has so far not turned up a "particular element" in the co-pilot's life which could explain his alleged action, he said.
Lufthansa CEO Carsten Spohr has said that Lubitz had suspended his pilot training, which began in 2008, "for a certain period", before restarting and qualifying for the Airbus A320 in 2013.
The second-in-command had passed all psychological tests required for training, Spohr told reporters.
Germany is to hold a national memorial ceremony on April 17 for the victims of the disaster, half of whom were German, with Spain accounting for at least 50 and the remainder composed of more than a dozen other nationalities.
France's Investigation and Analysis Bureau (BEA), tasked with investigating civil aviation accidents, meanwhile said it was "dismayed" by the revelations in the German press which it said smacked of "voyeurism".