An element from the damaged black box flight data recorder is seen in this photo released April 3, 2015 by the BEA, France's Bureau d'Enquetes et d'Analyses (Air Accident Investigator) from the Germanwings Airbus A320 crash. This second black box was discovered on the mountainside site where a Germanwings Airbus A320 crashed in the French Alps last week, killing all 150 people who were on board. The Marseille prosecutor said on Thursday that 150 sets of DNA had been found in the wreckage, corresponding to the number of passengers and crew on board the Airbus A320 jet that crashed on March 24.[Photo/Agencies]

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.

German prosecutors have said Lubitz's medical records from before he received his pilot's license referred to "suicidal tendencies," and Lufthansa, Germanwings' parent company, said it knew six years ago that Lubitz had had an episode of "severe depression" before he finished his flight training.

In Marseille, prosecutor Brice Robin said that his investigation focuses on France for now, but he has filed a formal request for judicial cooperation from Germany that could expand the scope of his probe.

Robin underlined French investigators' conviction that he was conscious until the moment of impact, and appears to have acted repeatedly to stop an excessive speed alarm from sounding.

"It's a voluntary action that guided this plane toward the mountain, not only losing altitude but correcting the aircraft's speed," he said Thursday.

The mountain rescue officer who found the data recorder, Alice Coldefy, described Friday the unexpected discovery in a spot that had already been repeatedly searched.