The co-pilot of the crashed Germanwings plane, Andreas Lubitz, had received treatment for suicidal tendencies before getting his pilot licence, investigators say, but not recently.
Lubitz, 27, is suspected of deliberately crashing the plane in the Alps, killing all 150 people on board.
Officials in Duesseldorf said the investigation to this point had revealed no clue to any motive.
So far, DNA strands of 80 of the victims have been found.
Duesseldorf public prosecutor Christoph Kumpa said that “several years” before Lubitz became a pilot he “had at that time been in treatment of a psychotherapist because of what is documented as being suicidal”.
But he added: “In the following period, and until recently, further doctor’s visits took place, resulting in sick notes without any suicidal tendencies or aggression against others being recorded.”
No specific dates were given. Lubitz enrolled in training with Lufthansa, which owns Germanwings, in 2008 and became a pilot in 2013. He was diagnosed with a serious depressive episode in 2009 and received treatment for a year and a half, media reports say.