Andreas Lubitz runs the Airportrace half marathon in Hamburg in this September 13, 2009 file photo. The co-pilot who appears to have deliberately crashed Germanwings plane carrying 149 passengers into the French Alps received psychiatric treatment for a "serious depressive episode" six years ago, German tabloid Bild reported on March 27, 2015. Prosecutors in France, after listening to the cockpit voice recorders, offered no motive for why Andreas Lubitz, 27, would take the controls of the Airbus A320, lock the captain out of the cockpit and deliberately set it veering down from cruising altitude at 3,000 feet per minute. [Photo/Agencies]

DUESSELDORF - German authorities said on Friday they had found torn-up sick notes showing that the pilot who crashed a plane into the French Alps was suffering from an illness that should have grounded him on the day of the tragedy.

French prosecutors believe Andreas Lubitz, 27, locked himself alone in the cockpit of the Germanwings Airbus A320 on Tuesday and deliberately steered it into a mountain, killing all 150 people on board.

"Documents with medical contents were confiscated that point towards an existing illness and corresponding treatment by doctors," said the prosecutors' office in Duesseldorf, where the co-pilot lived and where the doomed flight from Barcelona was heading.

Torn-up doctor's notes found in his home would have excused Lubitz from work for medical reasons, for a period that included the day of the crash. That supported the view that Lubitz had "hidden his illness from his employer and his colleagues", the prosecutors said.

They found no suicide note or confession, "nor was there any evidence of a political or religious background to what happened", they added.

Germanwings said Lubitz had not submitted any sick note that would have grounded him on Tuesday, March 24, the day of the crash.

In France, authorities said they had recovered between 400 and 600 body parts strewn across the Alpine crash site. No bodies were found intact and DNA testing would be the best way to identify the remains, Patrick Touron, deputy head of the criminal research division of France's Gendarmerie, told reporters at the site. Investigators would look for pieces of uniform to try to identify the crew including Lubitz.

Lubitz's mental health - and what Germanwings and parent company Lufthansa knew about it - could become central questions in any future legal case over the crash. Under German law, employees are required to inform their employers immediately if they are unable to work.

A hospital in Duesseldorf said Lubitz had visited to receive a diagnosis as recently as March 10. It would not give further details because of patient confidentiality rules but said media reports he was treated there for depression were inaccurate.

Reports in German media suggested Lubitz had suffered from depression in the past, and that Lufthansa would have been aware of at least some of that history.

Germany's Bild newspaper, citing internal documents forwarded by Lufthansa's Aero Medical Center to German authorities, reported that Lubitz had suffered a "serious depressive episode" around the time he suspended his pilot training in 2009. It said he subsequently spent over a year in psychiatric treatment.

Lufthansa and German prosecutors declined to comment on the report. The airline's CEO Carsten Spohr said on Thursday there was nothing in his past suggest Lubitz was a risk, and that after he resumed his training, he passed all tests with "flying colours".

An international agreement generally limits airline liability to around $157,400 for each passenger who dies in a crash, but if families can prove an airline was negligent they can pursue compensation for greater damages in lawsuits.