BERLIN - Germanwings copilot 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.

Dusseldorf 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 copilot 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 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 copilot 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 copilot 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 copilot'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.