BERLIN (AP) - Germanwings co-pilot Andreas Lubitz spent time online researching suicide methods and cockpit door security in the week before crashing Flight 9525, prosecutors said Thursday - the first evidence that the fatal descent may have been a premeditated act.

As the browsing history on a tablet computer found at Lubitz's apartment added a disturbing new piece to the puzzle of the March 24 crash, French investigators said they had recovered the Airbus A320's flight data recorder - another step toward completing the picture.

Attention has focused on Lubitz since investigators evaluated the plane's cockpit voice recorder last week. They believe the 27-year-old locked his captain out of the cockpit during the flight from Barcelona to Duesseldorf and deliberately plunged the plane into a French mountainside.

Duesseldorf prosecutors said they had reviewed search terms from March 16-23 that were in the browser memory of the computer found in Lubitz's home in the city.

The co-pilot researched "on one hand medical treatment methods, and on the other hand informed himself about types and ways of going about a suicide," prosecutors' spokesman Ralf Herrenbrueck said in a statement.

33 PHOTOS Germanwings - Andreas Lubitz pilot - memorials - plane crash See Gallery German crash co-pilot researched suicide, cockpit doors In this photo released today, co-pilot of Germanwings flight 4U9525 Andreas Lubitz participates in the Airport Hamburg 10-mile race on September 13, 2009 in Hamburg, Germany. Lubitz is suspected of having deliberately piloted Germanwings flight 4U 9525 into a mountain in southern France on March 24, 2015 and killing all 150 people on board, including himself, in the worst air disaster in Europe in recent history. (Photo by Getty Images) French authorities have indicated they believe the co-pilot of the GermanWings Airbus A320 deliberately took over the aircraft on Tuesday,crashing the plane on purpose and killing all 158 passengers and crew. The planned flight, from Barcelona to Dusseldorf, took a path over the southern French Alps near Dignes where the wreckage of the plane was found. At first GermanWings authorities expressed surprise and dismay in social media with the French authorities conclusion adding they believed it was too early in the investigation. A Lufthansa press conference later on Thursday, held in Germany, by Chief Executive Carsten Spohr stated that it appeared the co-pilot had prevented the pilot from entering the cockpit after a bathroom break. It leaves us absolutely speechless, he said. I wouldnt not have been able to imagine that the situation would have got even worse. ----- This social media photo of Andreas Lubitz near the Golden Gate Bridge in San Francisco was found on his Facebook Page. FRANKFURT, GERMANY - MARCH 14: (EXCLUSIVE COVERAGE) (EDITOR'S NOTE: This photo is available exclusively through Getty Images) In this photo released today, co-pilot of Germanwings flight 4U9525 Andreas Lubitz participates in the Frankfurt City Half-Marathon on March 14, 2010 in Frankfurt, Germany. Lubitz is suspected of having deliberately piloted Germanwings flight 4U 9525 into a mountain in southern France on March 24, 2015 and killing all 150 people on board, including himself, in the worst air disaster in Europe in recent history. (Photo by Getty Images) MONTABAUR, GERMANY - MARCH 26: A policeman carries bags out of the residence of the parents of Andreas Lubitz, co-pilot on Germanwings flight 4U9525, on March 26, 2015 in Montabaur, Germany. French authorities confirmed that Lubitz was alone in the cockpit during the rapid descent of flight 4U9525 until it crashed into mountains in southern France two days ago, killing all 150 people on board. Authorities are pursuing the possibility that Lubitz might have acted deliberately in steering the aircraft to is destruction. (Photo by Thomas Lohnes/Getty Images) MONTABAUR, GERMANY - MARCH 26: Police carry computer, a box and bags out of the residence of the parents of Andreas Lubitz, co-pilot on Germanwings flight 4U9525, on March 26, 2015 in Montabaur, Germany. French authorities confirmed that Lubitz was alone in the cockpit during the rapid descent of flight 4U9525 until it crashed into mountains in southern France two days ago, killing all 150 people on board. Authorities are pursuing the possibility that Lubitz might have acted deliberately in steering the aircraft to is destruction. (Photo by Thomas Lohnes/Getty Images) MONTABAUR, GERMANY - MARCH 26: Police carry computer, a box and bags out of the residence of the parents of Andreas Lubitz, co-pilot on Germanwings flight 4U9525, on March 26, 2015 in Montabaur, Germany. French authorities confirmed that Lubitz was alone in the cockpit during the rapid descent of flight 4U9525 until it crashed into mountains in southern France two days ago, killing all 150 people on board. Authorities are pursuing the possibility that Lubitz might have acted deliberately in steering the aircraft to is destruction. (Photo by Thomas Lohnes/Getty Images) COLOGNE, GERMANY - APRIL 17: Members of the public take part in a memorial service to commemorate the victims of the Germanwings flight 4U9525 passenger plane crash at the Dom cathedral on April 17, 2015 in Cologne, Germany. Approximately 1,400 people, including 500 family member of victims, will attend the service to pay their respects to the 149 victims killed when co-pilot Andreas Lubitz purposefully locked himself in the cockpit and piloted the plane at high speed into a mountainside in southern France on March 24, instantly killing everyone on board, including himself. (Photo by Pool/Getty Images) COLOGNE, GERMANY - APRIL 17: Lower Saxony Governor Stephan Weil (2nd R) attends a memorial service to commemorate the victims of the Germanwings flight 4U9525 passenger plane crash at the Dom cathedral on April 17, 2015 in Cologne, Germany. Approximately 1,400 people, including 500 family member of victims, will attend the service to pay their respects to the 149 victims killed when co-pilot Andreas Lubitz purposefully locked himself in the cockpit and piloted the plane at high speed into a mountainside in southern France on March 24, instantly killing everyone on board, including himself. (Photo by Pool/Getty Images) COLOGNE, GERMANY - APRIL 17: German President Joachim Gauck takes part in a memorial service to commemorate the victims of the Germanwings flight 4U9525 passenger plane crash at the Dom cathedral on April 17, 2015 in Cologne, Germany. Approximately 1,400 people, including 500 family member of victims, will attend the service to pay their respects to the 149 victims killed when co-pilot Andreas Lubitz purposefully locked himself in the cockpit and piloted the plane at high speed into a mountainside in southern France on March 24, instantly killing everyone on board, including himself. (Photo by Pool/Getty Images) COLOGNE, GERMANY - APRIL 17: A memorial of flowers and candles can be seen on the a memorial service to commemorate the victims of the Germanwings passenger plane crash, on April 17, 2015 in Cologne, Germany. Approximately 1,400 people, including 500 family member of victims, will attend the service to pay their respects to the 149 victims killed when co-pilot Andreas Lubitz purposefully locked himself in the cockpit and piloted the plane at high speed into a mountainside in southern France on March 24, instantly killing everyone on board, including himself. (Photo by Sascha Schuermann/Getty Images) COLOGNE, GERMANY - APRIL 17: A memorial of flowers and candles can be seen on the a memorial service to commemorate the victims of the Germanwings passenger plane crash, on April 17, 2015 in Cologne, Germany. Approximately 1,400 people, including 500 family member of victims, will attend the service to pay their respects to the 149 victims killed when co-pilot Andreas Lubitz purposefully locked himself in the cockpit and piloted the plane at high speed into a mountainside in southern France on March 24, instantly killing everyone on board, including himself. (Photo by Sascha Schuermann/Getty Images) COLOGNE, GERMANY - APRIL 17: People watch the ecumenical memorial service to commemorate the victims of the Germanwings passenger plane crash, on April 17, 2015 in Cologne in front of the Cologne, Germany. Approximately 1,400 people, including 500 family member of victims, will attend the service to pay their respects to the 149 victims killed when co-pilot Andreas Lubitz purposefully locked himself in the cockpit and piloted the plane at high speed into a mountainside in southern France on March 24, instantly killing everyone on board, including himself. (Photo by Sascha Schuermann/Getty Images) COLOGNE, GERMANY - APRIL 17: A memorial of flowers and candles can be seen on the a memorial service to commemorate the victims of the Germanwings passenger plane crash, on April 17, 2015 in Cologne, Germany. Approximately 1,400 people, including 500 family member of victims, will attend the service to pay their respects to the 149 victims killed when co-pilot Andreas Lubitz purposefully locked himself in the cockpit and piloted the plane at high speed into a mountainside in southern France on March 24, instantly killing everyone on board, including himself. (Photo by Sascha Schuermann/Getty Images) COLOGNE, GERMANY - APRIL 17: Guests arrive for a memorial service to commemorate the victims of the Germanwings passenger plane crash, on April 17, 2015 in Cologne, Germany. Approximately 1,400 people, including 500 of the victims' relatives, will attend the service to pay their respects to the 149 victims who were killed when co-pilot Andreas Lubitz purposefully locked himself in the cockpit and piloted the plane at high speed into a mountainside in southern France on March 24, instantly killing everyone on board, including himself. (Photo by Sascha Schuermann/Getty Images) COLOGNE, GERMANY - APRIL 17: A black ribbon showing the flight number of Germanwings flight 4U9525 is displayed at the Dom cathedral, ahead of a memorial service to commemorate the victims of the Germanwings passenger plane crash, on April 17, 2015 in Cologne, Germany. Approximately 1,400 people, including 500 family member of victims, will attend the service to pay their respects to the 149 victims killed when co-pilot Andreas Lubitz purposefully locked himself in the cockpit and piloted the plane at high speed into a mountainside in southern France on March 24, instantly killing everyone on board, including himself. (Photo by Sascha Schuermann/Getty Images) COLOGNE, GERMANY - APRIL 17: North Rhine-Westphalia Governor Hannelore Kraft and Lufthansa CEO Carsten Spohr, ahead of a memorial service to commemorate the victims of the Germanwings passenger plane crash, on April 17, 2015 in Cologne, Germany. Approximately 1,400 people, including 500 of the victims' relatives, will attend the service to pay their respects to the 149 victims who were killed when co-pilot Andreas Lubitz purposefully locked himself in the cockpit and piloted the plane at high speed into a mountainside in southern France on March 24, instantly killing everyone on board, including himself. (Photo by Sascha Schuermann/Getty Images) Germanwings chief operating officer (COO) and member of the board Oliver Wagner holds a press conference on March 30, 2015 in Marseille, southern France about the creation of a family assistance center for the relatives of victims of a Germanwings flight that crashed in the French Alps, killing all 150 aboard. French prosecutors believe that co-pilot Andreas Lubitz locked his captain out of the cockpit and deliberately flew Flight 4U 9525 into a mountainside near Seyne-les-Alpes. AFP PHOTO / BERTRAND LANGLOIS (Photo credit should read BERTRAND LANGLOIS/AFP/Getty Images) DIGNE-LES-BAINS, FRANCE - MARCH 28: Bishop Jean-Philippe Nault (C) leads a service for local residents remembering the victims of Germanwings Airbus fight near the crash site at Notre Dame du Bourg cathedral on March 28, 2015 in Digne-les-Bains, France. French authorities confirmed that Andreas Lubitz was alone in the cockpit during the rapid descent of flight 4U9525 until it crashed into mountains in southern France four days ago, killing all 150 people on board. Lubitz hid signs of illness and it is thought he acted deliberately in steering the aircraft to its destruction. (Photo by Thomas Lohnes/Getty Images) LA VERNET, FRANCE - MARCH 28: Relatives stand at a monument to honour the victims of Germanwings flight 4U9525 in front of the mountains near the crash site on March 26, 2015 in Le Vernet, France. France. French authorities confirmed that Andreas Lubitz was alone in the cockpit during the rapid descent of flight 4U9525 until it crashed into mountains in southern France four days ago, killing all 150 people on board. Lubitz hid signs of illness and it is thought he acted deliberately in steering the aircraft to its destruction. (Photo by Thomas Lohnes/Getty Images) LA VERNET, FRANCE - MARCH 28: Relatives stand at a monument to honour the victims of Germanwings flight 4U9525 in front of the mountains near the crash site on March 26, 2015 in Le Vernet, France. France. French authorities confirmed that Andreas Lubitz was alone in the cockpit during the rapid descent of flight 4U9525 until it crashed into mountains in southern France four days ago, killing all 150 people on board. Lubitz hid signs of illness and it is thought he acted deliberately in steering the aircraft to its destruction. (Photo by Thomas Lohnes/Getty Images) A helicopter of the French gendarmerie flies over Seyne-les-Alpes on March 28, 2015, near the site where a Germanwings flight crashed in the French Alps, killing all 150 aboard. French prosecutors believe that co-pilot Andreas Lubitz locked his captain out of the cockpit and deliberately flew Flight 4U 9525 into a mountainside near Seyne. AFP PHOTO / JEFF PACHOUD (Photo credit should read JEFF PACHOUD/AFP/Getty Images) A helicopter of the French gendarmerie flies over Seyne-les-Alpes on March 28, 2015, near the site where a Germanwings flight crashed in the French Alps, killing all 150 aboard. French prosecutors believe that co-pilot Andreas Lubitz locked his captain out of the cockpit and deliberately flew Flight 4U 9525 into a mountainside near Seyne. AFP PHOTO / JEFF PACHOUD (Photo credit should read JEFF PACHOUD/AFP/Getty Images) Flowers and candles have been left to commemorate a woman, a victim of the Germanwings plane crash from Halle, eastern Germany on March 28, 2015. French prosecutors believe that co-pilot Andreas Lubitz locked his captain out of the cockpit and deliberately flew Flight 4U 9525 into a mountainside near Seyne. AFP PHOTO / DPA / HENDRIK SCHMIDT +++ GERMANY OUT +++ (Photo credit should read HENDRIK SCHMIDT/AFP/Getty Images) LE VERNET, FRANCE - MARCH 28: Policemen stand in front of a memorial stone for the victims of the Germanwings Airbus flight near to the crash site on March 28, 2015 in Le Vernet, France. French authorities confirmed that Andreas Lubitz was alone in the cockpit during the rapid descent of flight 4U9525 until it crashed into mountains in southern France four days ago, killing all 150 people on board. Lubitz hid signs of illness and it is thought he acted deliberately in steering the aircraft to its destruction. (Photo by Thomas Lohnes/Getty Images) LE VERNET, FRANCE - MARCH 28: Policemen stand in front of a memorial stone for the victims of the Germanwings Airbus flight near to the crash site on March 28, 2015 in Le Vernet, France. French authorities confirmed that Andreas Lubitz was alone in the cockpit during the rapid descent of flight 4U9525 until it crashed into mountains in southern France four days ago, killing all 150 people on board. Lubitz hid signs of illness and it is thought he acted deliberately in steering the aircraft to its destruction. (Photo by Thomas Lohnes/Getty Images) A candle is lit in front of a board with the flight number of Germanwings plane 4U92524 and the lettering 'We are in mourning' in English, German and Spanish during the annual general meeting of Lufthansa Group at the Congress Center in Hamburg, northern Germany, on April 29, 2015. German airline Lufthansa holds it annual shareholders' meeting in the shadow of last month's Germanwings crash in the French Alps which killed 150 people. AFP PHOTO / CARMEN JASPERSEN (Photo credit should read CARMEN JASPERSEN/AFP/Getty Images) COLOGNE, GERMANY - APRIL 17: A memorial of flowers and candles can be seen on the a memorial service to commemorate the victims of the Germanwings passenger plane crash, on April 17, 2015 in Cologne, Germany. Approximately 1,400 people, including 500 family member of victims, will attend the service to pay their respects to the 149 victims killed when co-pilot Andreas Lubitz purposefully locked himself in the cockpit and piloted the plane at high speed into a mountainside in southern France on March 24, instantly killing everyone on board, including himself. (Photo by Sascha Schuermann/Getty Images) A program and a carving of wood are seen during the memorial service for the 150 people killed in the Germanwings plane crash in the Cathedral in Cologne, western Germany on April 17, 2015. About 1,500 guests are expected for the service, among them 500 relatives of the victims, in northern Europe's largest Gothic church, which will also be broadcast livCe on screens outside the cathedral and to viewers nationwide. AFP PHOTO / POOL / OLIVER BERG (Photo credit should read OLIVER BERG/AFP/Getty Images) Anonymous stand near a stela commemorating the victims of the March 24 Germanwings Airbus A320 crash in the village of Le Vernet, southeastern France, on April 6, 2015 after a ceremony with victims' relatives. A German Airbus A320 of the low-cost carrier Germanwings crashed in the French Alps on March 24, killing all 150 people on board. AFP PHOTO / JEAN CHRISTOPHE MAGNENET (Photo credit should read JEAN CHRISTOPHE MAGNENET/AFP/Getty Images) People mourn at the memorial of flowers and candles in front of the Joseph-Koenig-Gymnasium secondary school in Haltern am See, western Germany on April 1, 2015, from where some of the Germanwings plane crash victims came. A church service will take place in the small western German town of Haltern to remember 16 pupils and two teachers from the same school who were killed in the Germanwings air disaster as they returned from an exchange trip to Barcelona. AFP PHOTO / SASCHA SCHUERMANN (Photo credit should read SASCHA SCHUERMANN/AFP/Getty Images) National flags of countries of the victims, a teddy bear, books and different items put by people, are pictured near a stele in memory of the victims of the Germanwings Airbus A320 crash, in Seyne-les-Alpes, French Alps, on March 30, 205. Investigators sifting through the wreckage of the doomed plane in the French Alps were forced on March 30 to resume the hunt on foot as bad weather hampered helicopter flights. AFP PHOTO / JEAN-PERRE CLATOT (Photo credit should read JEAN-PIERRE CLATOT/AFP/Getty Images) A stone reading 'RIP 4U 9525 in deep sorrow' lays amidst a memorial of flowers and candles in front of the headquarters of German airline Germanwings in Cologne, western Germany, on March 30, 2015. Officials say that the co-pilot of a Germanwings A320 Airbus plane that crashed on March 24, 2015 in the French Alps locked the captain out of the cockpit of the Airbus jet and deliberately crashed Flight 4U 9525, bound for Duesseldorf from Barcelona. The plane is said to have crashed at a speed of 700 kilometres (430 miles) per hour, killing all 150 on board instantly. AFP PHOTO / DPA / OLIVER BERG +++ GERMANY OUT (Photo credit should read OLIVER BERG/AFP/Getty Images) A general view of the University hospital were Andreas Lubitz, the Germanwings co-pilot who flew his Airbus into a French mountainside, had been treated, is pictured on March 27, 2015, in Duesseldorf, western Germany. Andreas Lubitz, the co-pilot who French authorities say appeared to deliberately crash a Germanwings flight, was a life-long flying enthusiast with no apparent psychological problems or terrorist links. into the French Alps, killing all 150 aboard, hid a serious illness from the airline, prosecutors said Friday amid reports he was severely depressed. AFP PHOTO / PATRIK STOLLARZ (Photo credit should read PATRIK STOLLARZ/AFP/Getty Images) Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

"In addition, on at least one day, (Lubitz) concerned himself for several minutes with search terms about cockpit doors and their security precautions," he added.

Prosecutors didn't specify what medical treatment Lubitz was looking into and declined to disclose the individual search terms that he used. They said personal correspondence and search terms on the tablet "support the conclusion that the machine was used by the co-pilot in the relevant period."

In Marseille, prosecutor Brice Robin underlined French investigators' conviction that "he was alive until the moment of impact, we are nearly certain. ... Alive and conscious." He also said the co-pilot appears to have acted repeatedly to stop an excessive speed alarm from sounding.

He said investigators had found 150 DNA profiles - matching the number of people aboard the plane - but it will take time to match them with DNA samples provided by victims' families.

Investigators hope the flight data recorder will reveal more information on what happened to the plane and the co-pilot's actions at the controls. Robin said it was found by a gendarme buried on the side of a ravine that was "already explored several times."

The flight data recorder was "completely blackened" as though it had been burned, but it was "possibly usable," Robin said. It captures 25 hours of information on the position and condition of nearly every part of the plane.

German prosecutors have said Lubitz's medical records from before he received his pilot's license referred to "suicidal tendencies," but visits to doctors since then showed no record of that or aggression toward others.

Investigators also found torn-up notes from doctors excusing Lubitz from work, including one that would have kept him off work on the day of the crash.

Earlier this week, Lufthansa, Germanwings' parent company, said it knew six years ago that Lubitz had suffered from an episode of "severe depression" before he finished his flight training.

However, Germanwings, which hired Lubitz in September 2013, said Thursday it had been unaware of the depressive episode.

Prosecutors have said that they haven't found any sign of a physical illness and have no evidence he told anyone what he was going to do.

Also Thursday, Germany announced the creation of an expert task force to examine what went wrong and consider whether changes are needed regarding cockpit doors, how pilots pass medical evaluations and how companies recognize psychological problems in employees.

France's air accident investigation agency is already examining cockpit entry and psychological screening procedures.

The A320 is designed with safeguards to allow emergency entry into the cockpit if a pilot inside is unresponsive. But the override code known to the crew doesn't go into effect if the person in the cockpit specifically denies entry.

The impact of the crash shattered the plane into tiny pieces. Robin said that investigators have found and studied 2,854 body parts at the site.

They also found 42 cellphones in what Robin called a "very, very damaged" condition.

No video or audio from the cellphones of those aboard the plane has been released publicly. However, a French reporter says he viewed video from one cellphone video thanks to an intermediary close to the crash investigation, although he does not have a copy of it himself.

Frederic Helbert, who reported on the video this week in the French magazine Paris-Match and the German tabloid Bild, told The Associated Press that it was shot from the back of the plane, so "you cannot see their faces, but you can hear them screaming and screaming."

"No one is moving or getting up," he told the AP in Paris. "People understand something terrible is going to happen."

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Associated Press writers Elaine Ganley and Angela Charlton in Paris and Frank Jordans in Berlin contributed to this report.