DUSSELDORF (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.

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 Dusseldorf flight's eight-minute descent after he left to use the toilet.

The mass-circulation'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".

Bild said that earlier on in Tuesday's flight the captain was heard explaining to his colleague that he had not had time to go to the toilet before take-off.

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 Dusseldorf 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.

Meanwhile, helicopters resumed search operations at the crash zone in southeastern France for a sixth day early Sunday, an AFP reporter saw, as efforts to comb the area for the victims' remains and a second black box continue.

"There's no reason not to find the second black box," French investigator Xavier Vialenc told AFP Saturday.