The BEA agency issued a statement Friday, one day after officials announced that the plane’s black box data recorder had been found.
According to investigators, initial readings of the recorder show that the pilot used the automatic pilot to put the plane into a descent -- then repeatedly adjusted the automatic pilot during descent to speed up the plane.
The officials said they had recovered a tablet computer from Lubitz's home that had been used between March 16 and 23, the day before the crash. Kumpa said Lubitz, 27, had also used the tablet to do research for ways to carry out suicide -- suggesting a degree of premeditation.
The Germanwings plane that departed from Barcelona crashed en route to Dusseldorf on March 24 with all 150 people on board killed on impact.
German authorities previously said Lubitz had been treated by a psychotherapist because of previous suicidal tendencies and that he had deliberately flown the jetliner into a mountain.
The Associated Press contributed to this report.