Germanwings co-pilot Andreas Lubitz appears to have hidden evidence of an illness from his employers, including having been excused by a doctor from work the day he crashed a passenger plane into a mountain, prosecutors said.
The evidence came from the search of Lubitz's homes in two German cities for an explanation why he crashed the Airbus A320 into the French Alps, killing all 150 people on board.
Prosecutor's spokesman Ralf Herrenbrueck said torn-up sick notes for the day of the crash "support the current preliminary assessment that the deceased hid his illness from his employer and colleagues".
Such sick notes from doctors excusing employees from work are common in Germany and issued even for minor illnesses. Mr Herrenbrueck did not reveal details of what illness Lubitz was suffering from.
He said other medical documents found indicated "an existing illness and appropriate medical treatment", but that no suicide note was found. He added there was no indication of any political or religious motivation for Lubitz's actions.
Germanwings, a subsidiary of Lufthansa, refused to comment on the new information.
Investigators had removed multiple boxes of items from Lubitz's apartment in Dusseldorf and his parents' house in Montabaur, near Frankfurt.
A German aviation official said Lubitz's file at the country's Federal Aviation Office contained an "SIC" note, meaning he needed "specific regular medical examination". Such a note could refer to either a physical or mental condition, but the official said the note does not specify which.
However, neighbours described a man whose physical health was superb.
"He definitely did not smoke. He really took care of himself. He always went jogging. I am not sure whether he did marathons, but he was very healthy," said Johannes Rossmann, who lived a few doors down from Lubitz's home in Montabaur.
German news media painted a picture of a man with a history of depression who had received psychological treatment, and who might have been set off by a falling-out with his girlfriend. Dusseldorf prosecutors, who are leading the German side of the probe, refused to comment on the anonymously sourced reports, citing the continuing investigation.
Lufthansa chief executive Carsten Spohr said there was a "several-month" gap in Lubitz's training six years ago, but would not elaborate. Following the disruption, he said, Lubitz "not only passed all medical tests but also his flight training, all flying tests and checks".
The US Federal Aviation Administration had issued Lubitz a third-class medical certificate. To obtain a certificate, a pilot must be cleared of psychological problems including psychosis, bipolar disorder and personality disorder "severe enough to have repeatedly manifested itself by overt acts".
The certificate also means he was not found to be suffering from another mental health condition that "makes the person unable to safely perform the duties or exercise the privileges" of a pilot's licence.
French investigators, who are in charge of the probe into the plane crash, believe the 27-year-old locked himself inside the cockpit and intentionally smashed the Germanwings plane into a mountainside on Tuesday during a flight from Barcelona to Dusseldorf.
People in Montabaur who knew Lubitz said they were shocked at the allegations that he could have intentionally crashed the plane, saying he had been thrilled with his job at Germanwings and seemed to be "very happy".
Germanwings, a low-cost carrier in the Lufthansa Group, said it was setting up a family assistance centre in Marseille for relatives of those killed in the crash.
"In these dark hours our full attention belongs to the emotional support of the relatives and friends of the victims of Flight 9525," Germanwings chief executive Thomas Winkelmann said.
Dusseldorf University Hospital said Lubitz had been treated as a patient there over the past two months.
A statement said Lubitz last attended for "diagnostic clarifications" on March 10.
It declined to provide details about his condition but denied reports that it had treated the 27-year-old for depression.
The hospital said it had submitted Lubitz's medical file to prosecutors in Dusseldorf.
Professor Klaus Hoeffken, medical director and chief executive of the hospital, said: "We would like to express our shock and disbelief about the tragedy. We will support the investigation emphatically and without reservations. We send our deepest condolences to the relatives of the victims of the plane catastrophe."