Marseille, France (CNN) Initial tests on the flight data recorder recovered from downed Germanwings Flight 9525 show that co-pilot Andreas Lubitz purposely used the controls to speed up the plane's descent, according to the French air accident investigation agency, the BEA.

The flight data recorder, or "black box," was found Thursday by recovery teams that have spent days since the March 24 crash scouring the mountainside in the French Alps where the plane went down.

A statement from the BEA on Friday said its teams had immediately begun to investigate its contents.

"The initial readout shows that the pilot present in the cockpit used the autopilot to put the (airplane) into a descent towards an altitude of 100 (feet) then, on several occasions during the descent, the pilot modified the autopilot setting to increase the speed of the (airplane) in descent," it said.

"Work is continuing to establish the precise history of the flight."

Evidence from the plane's cockpit voice recorder, recovered swiftly after the crash, had already led investigators to believe that Lubitz acted deliberately to bring down the plane, killing all 150 people on board.

And prosecutors in Germany said Thursday that an analysis of a tablet device retrieved from the 27-year-old's apartment in Dusseldorf revealed that he had researched suicide methods and cockpit door security on the Internet.

The correspondence and search history on the device demonstrated that the co-pilot used it from March 16 to March 23, Dusseldorf prosecutor Christoph Kumpa said.

The search history was not deleted and also revealed searches concerning medical treatment, the prosecutor said.

DNA profiles

Investigators have focused on Lubitz's health as they try to establish his motivation.

But the missing "black box" was expected to yield important evidence about the plane's final minutes.

A female police officer digging by hand for clothes in a ravine that been searched previously found the flight data recorder Thursday afternoon about 8 inches (20 centimeters) below the surface, Marseille prosecutor Brice Robin told reporters.

Usually white with florescent orange, this discovered recorder lived up to its name as a black box because fire had darkened it with ashes.

In addition, out of more than 2,000 DNA samples collected from the crash site, lab workers have isolated 150 DNA profiles, Robin told reporters.

"That does not mean we've identified" the crash's 150 victims, Robin said -- noting the recovered DNA still must be compared with DNA submitted by the families of those who died in the crash.

Authorities have also found 470 personal effects at the site, according to Robin. That number includes 40 cell phones, though all those were badly damaged. Robin cast doubt that any useful information could be retrieved from those phones, given their condition.

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That view is consistent with French officials' claims Wednesday insisting that two publications, German daily Bild and French Paris Match, were wrong to report that cell phone video showed the harrowing final seconds from on board the flight.

'Premeditated murder' claim

Noting he's made a criminal request to German authorities but is for now conducting his own investigation, the French prosecutor said he is tasked with an involuntary homicide investigation.

But Robin noted that Lubitz made voluntary actions -- such as guiding the plane toward the mountain and reducing its speed to prevent alarms from going off -- and was "alive and conscious" to the very end.

A European official government official with detailed knowledge of the investigation said that Lubitz's actions amount to "premeditated murder."

While cautioning that there are still many holes in understanding Lubitz's motivation, the disclosures about his Internet searches show that he planned to do what he was going to do, according to this official.

Source: Lubitz saw multiple doctors

It is becoming increasingly clear to investigators that Lubitz was "very afraid" he would lose his license to fly because of his medical issues, a law enforcement source with detailed knowledge of the investigation told CNN on Thursday.

It's already emerged that Lubitz had battled depression years before he took the controls of Flight 9525 and that he had concealed from his employer recent medical leave notes saying he was unfit for work.

But the law enforcement source said that after a severe depressive episode in 2009, Lubitz relapsed with severe depression and stress in late 2014.

In the weeks leading up to the crash, Lubitz was shopping doctors, seeing at least five, perhaps as many as six, the source said, as he kept going from one doctor to the next seeking help, including from a sleep specialist. He was prescribed powerful medication, though it's not clear he was taking it.

Photos: Germanwings plane crashes in France A recovery crew works among debris of Germanwings Flight 9525 at the crash site near Seyne-les-Alpes, France, on Friday, April 3. The crash killed all 150 people aboard and has raised questions about the co-pilot's mental state. Hide Caption 1 of 26 Photos: Germanwings plane crashes in France French Gen. David Galtier holds up a picture of the second black box from Germanwings 9525 during a news conference in Marseille, France, on Thursday, April 2. The flight data recorder shows that co-pilot Andreas Lubitz purposely used the controls to speed up the plane's descent, investigators said. Hide Caption 2 of 26 Photos: Germanwings plane crashes in France Rescue workers recover debris from the crash site in the French Alps on Tuesday, March 31. Flight 9525 was traveling from Barcelona, Spain, to Dusseldorf, Germany, when it crashed. Hide Caption 3 of 26 Photos: Germanwings plane crashes in France A helicopter drops rescue workers next to crash debris near Seyne-les-Alpes, France, on Sunday, March 29. Hide Caption 4 of 26 Photos: Germanwings plane crashes in France Forensic experts work near the crash site on Thursday, March 26. Hide Caption 5 of 26 Photos: Germanwings plane crashes in France Journalists stand in front of the Westerwald airfield in Montabaur, Germany, on March 27. Lubitz reportedly learned to fly here. Hide Caption 6 of 26 Photos: Germanwings plane crashes in France Investigators carry a computer from the home of Lubitz's parents in Montabaur, Germany, on Thursday, March 26. Hide Caption 7 of 26 Photos: Germanwings plane crashes in France A police officer stands guard March 26 at an apartment building where Lubitz was thought to have lived in Dusseldorf. Hide Caption 8 of 26 Photos: Germanwings plane crashes in France A helicopter lifts a rescue worker from the crash site on March 26. Hide Caption 9 of 26 Photos: Germanwings plane crashes in France Rescue workers continue to search the site of the crash on March 26. Hide Caption 10 of 26 Photos: Germanwings plane crashes in France Search-and-rescue teams land near the crash site on Wednesday, March 25. Hide Caption 11 of 26 Photos: Germanwings plane crashes in France Debris from the plane is seen along a mountainside on March 25. Hide Caption 12 of 26 Photos: Germanwings plane crashes in France French military personnel move up a mountainside March 25 near Seyne-les-Alpes. Hide Caption 13 of 26 Photos: Germanwings plane crashes in France The cockpit voice recorder of the Germanwings jet appears in this photo provided by the French air accident investigation bureau on March 25. The device is designed to capture all sounds on a plane's flight deck. Hide Caption 14 of 26 Photos: Germanwings plane crashes in France A helicopter comes in to land near Seyne-les-Alpes, the staging ground for search efforts, on March 25. Hide Caption 15 of 26 Photos: Germanwings plane crashes in France Rescue workers and members of the French Gendarmerie gather in Seyne-les-Alpes on Tuesday, March 24, as search-and-rescue teams struggle to reach the remote crash. Hide Caption 16 of 26 Photos: Germanwings plane crashes in France Wreckage is seen at the crash site on March 24. Hide Caption 17 of 26 Photos: Germanwings plane crashes in France Response teams gather in Seyne-les-Alpes on March 24. Hide Caption 18 of 26 Photos: Germanwings plane crashes in France Relatives of the flight's passengers arrive at the airport in Barcelona on March 24. Hide Caption 19 of 26 Photos: Germanwings plane crashes in France People hold hands walking through the Dusseldorf Airport on March 24. Hide Caption 20 of 26 Photos: Germanwings plane crashes in France The arrivals board at the Dusseldorf Airport shows Germanwings Flight 9525 without a status on March 24. Hide Caption 21 of 26 Photos: Germanwings plane crashes in France People arrive at the Dusseldorf Airport on March 24. Hide Caption 22 of 26 Photos: Germanwings plane crashes in France An employee of Swissport, the handling agent of Germanwings flights from Barcelona, speaks by phone at the Barcelona-El Prat Airport on March 24. Hide Caption 23 of 26 Photos: Germanwings plane crashes in France Relatives of people involved in the crash arrive at the Barcelona airport on March 24. Hide Caption 24 of 26 Photos: Germanwings plane crashes in France A man in Madrid looks at a monitor with a map, released from the Flightradar24 website, showing the point where the plane's radar signal went missing. Hide Caption 25 of 26 Photos: Germanwings plane crashes in France This undated file photo shows the Germanwings Airbus A320 that crashed. Germanwings is a low-cost airline owned by the Lufthansa Group. Hide Caption 26 of 26