Germanwings co-pilot Andreas Lubitz ripped up a doctor’s note excusing him from work on the day he crashed a crowded passenger plane into a mountain, according to prosecutors Friday, and was undergoing treatment at a German hospital where doctors last saw him two weeks before the crash.

University Hospital Dusseldorf acknowledged treating Lubitz but dismissed as "incorrect" media reports that it was for depression. The facility refused to say what Lubitz was being treated for, citing patient confidentiality. 

The hospital said Friday Lubitz visited the clinic for “diagnostic clarifications” in February and, most recently, on March 10.

Prosecutors in Germany reported Friday that Lubitz was being treated for a medical illness that he hid from his employer. Investigators found torn-up doctor's notes, including one declaring Lubitz unfit for work on the day of the crash, and other papers in searches at the home of his parents and at an apartment he kept in Dusseldorf. The evidence could provide clues as to why he apparently deliberately crashed the Airbus A320 into the French Alps Tuesday morning, killing all 150 people on board.

Dusseldorf prosecutor Christoph Kumpa said the doctor's note for the day of the crash indicated the co-pilot "was declared by a medical doctor unfit to work."

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Kumpa's spokesman Ralf Herrenbrueck said in a written statement that the note "support[s] the current preliminary assessment that the deceased hid his illness from his employer and colleagues."

Herrenbrueck said investigators did not find a suicide note or a letter claiming evidence of a political or religious background leading up to the event.

But the documents seized were of a medical content, that indicated "an existing disease and appropriate medical treatment," he said.

Such sick notes from doctors excusing employees from work are common in Germany and issued even for minor illnesses. Herrenbrueck didn't reveal details of what illness Lubitz was suffering from.

Germanwings, a subsidiary of Lufthansa, said it knew nothing about the doctor's note. "Currently there is media coverage that the co-pilot of Flight 9525 was given a sick note for the day of the accident on Tuesday," the airline said. "Germanwings declares that a sick note for this day was not submitted to the company."

The news from the German prosecutors came as questions were raised about whether the 27-year-old was mentally fit to be at the controls of the tragic flight--and if a break-up triggered his criminal actions.

On Friday, the German newspaper Bild, citing police and airline sources, published what it claimed were details of Lubitz's medical records. The paper claimed that Lubitz had been designated as "not suitable for flying" by his instructors at Lufthansa's training school in Arizona around the time that he halted his pursuit of a pilot's license in 2009. 

Bild reported that Lubitz spent 18 months receiving psychiatric treatment, was diagnosed with a "severe depressive episode," and received what it called a "special regular medical examination." The report added that investigators were examining whether Lubitz was suffering from a "personal life crisis" over a recent break-up with his girlfriend that left him heartbroken and in despair.

Whatever the status of his romance, another report Friday in a German magazine said it did not prevent Lubitz from walking into a Dusseldorf dealer just a few weeks ago and buying two new expensive Audi cars—one for himself and the other for the girlfriend, described as a teacher. Focus Online reported Lubitz took delivery of one of the cars last Saturday. The magazine said it was unclear which of the cars was delivered.

On Thursday French prosecutors stunned the world by announcing their conclusion that Lubitz deliberately crashed the Airbus A320 into a mountainside 65 miles north of Nice. In the process, investigators said, Lubitz locked the more experienced captain out of the cockpit and switched the aircraft's autopilot to its lowest descent setting while ignoring frantic calls from air traffic controllers--and the screams of terrified passengers.

Prosecutors said pilot Patrick Sonderheimer frantically tried to get back in the cabin before the plane hit the mountain at 430 miles per hour. Bild reported that a desperate Sonderheimer tried to break down the cockpit's door with an axe.

At the Germanwings crash site Friday, police said they had recovered between 400 and 600 pieces of remains so far from the 150 people who died.

Speaking from the remote town of Seyne, Col. Patrick Touron of the gendarme service said "we haven't found a single body intact." Officials have said the impact caused the jet to break into pieces no bigger than a small car. 

At Lufthansa headquarters, the airline said it would now require two crew members in a cockpit at all times, a rule already in place in the U.S. The company was criticized a day earlier after the CEO Carsten Spohr said he saw no need to make a change.  

The Lubitz apartment in Dusseldorf has two names on the letterbox. The Daily Telegraph reported that at one point, a man was led out of a home in Montabaur where the parents of Lubitz lived. The man was accompanied by police who used their jackets to shield him from the waiting media. 

The Bild report about Lubitz's battle with depression may shed new light on a relatively mysterious period in Lubitz's training to become a pilot. Lufthansa chief executive Carsten Spohr told reporters Thursday that Lubitz had taken a months-long break from his training, but did not explain why. 

"He passed all the subsequent tests and checks with flying colors," Spohr said. "His flying abilities were flawless." 

On Thursday, the German magazine Der Spiegel quoted friends of Lubitz as saying the pilot had taken a break from training because of depression and burnout. After completing his training, Lubitz spent an 11-month waiting period working as a flight attendant before becoming a co-pilot with Germanwings, Lufthansa's budget subsidiary, in September 2013. Spohr said such a waiting period is not unusual at Lufthansa.

The chairman of the glider club Lubitz frequented as a teenager in Montabaur told the Associated Press he rejected the French prosecutors' conclusion.

"I don't see how anyone can draw such conclusions before the investigation is completed," Klaus Radke said.

Another club member, Peter Ruecker, who had know Lubitz since his teen years, described him as "happy he had the job with Germanwings and he was doing well ... He was very happy. He gave off a good feeling."

""He seemed very enthusiastic" about his career, Ruecker added. "I can't remember anything where something wasn't right."

The Associated Press contributed to this report.