Germanwings co-pilot Andreas Lubitz appears to have hidden evidence of an illness from his employer and had been excused by a doctor from work the day he crashed a passenger plane into a mountain, prosecutors said Friday.

The statement follows a search of Lubitz's homes in two German cities for an explanation of why he crashed the Airbus A320 into the French Alps on Tuesday, killing all 150 people on board.

Lubitz house

A police officer carries bags out of the home of Andreas Lubitz's parents in Montabaur, Germany on Thursday. (Thomas Lohnes/Getty Images)

Prosecutors didn't say what type of illness — mental or physical — Lubitz may have been suffering from. German media reported Friday that the 27-year-old had received prolonged treatment starting in 2008 for a "serious depressive episode."

Duesseldorf prosecutors' office spokesman Ralf Herrenbrueck said in a written statement that torn-up sick notes, including one 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.

Herrenbrueck 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.

New 2 crew in cockpit rule

Germanwings and its parent company Lufthansa declined immediately to comment on the new information. But Lufthansa did announce that its airliners will introduce the two-person in the cockpit rule "as soon as possible" in consultation with their regulators.

Canadian airlines were ordered on Thursday to maintain two crew in the cockpit at all times, effective immediately. Many U.S. airlines already have a "rule of two" requiring that if one pilot leaves the cockpit another crew member, such as a flight attendant, must be in the cockpit as a replacement.

In the U.S., Federal Aviation Administration rules already require that two people must be in the cockpit at all times.

Investigators had removed multiple boxes of items from Lubitz's apartment in Duesseldorf and his parents' house in Montabaur, near Frankfurt.

A German aviation official told The Associated Press that Lubitz's file at the country's Federal Aviation Office contained an "SIC" note, meaning that he needed "specific regular medical examination." Such a note could refer to either a physical or mental condition, but the official — who would only speak anonymously, said the note does not specify which.

Jogger, never smoked

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.

ADDITION Germany France Plane Crash

Police searched the Dusseldorf apartment of Germanwings co-pilot Andreas Lubitz on Thursday. (Martin Meissner/Associated Press)

German news media painted a picture of a man with a history of depression who had received psychological treatment, and who may have been set off by a falling out with his girlfriend. Duesseldorf prosecutors, who are leading the German side of the probe, refused to comment on the anonymously sourced reports, citing the ongoing investigation.

Lufthansa CEO 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."

"Six years ago there was a lengthy interruption in his training. After he was cleared again, he resumed training. He passed all the subsequent tests and checks with flying colours. His flying abilities were flawless," Spohr said.

Months of psychiatric treatment

The German tabloid Bild, citing internal documents and Lufthansa sources Friday, said Lubitz spent a total of one-and-a-half years in psychiatric treatment at the time and that the relevant documents would be passed to French investigators once they had been examined by German authorities.

The U.S. Federal Aviation Administration had issued Lubitz a third-class medical certificate. In order to obtain such a certificate, a pilot must be cleared of psychological problems including psychosis, bipolar disorder and personality disorder "that is severe enough to have repeatedly manifested itself by overt acts."

The certificate also means that he wasn't 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.

Experts say it's possible that someone with mental health problems could have hidden them from employers or a doctor without specialist training.

"It's a high-stakes situation for pilots because they know if they give the wrong answer, they could lose their licence," said Dr. Raj Persaud, fellow of Britain's Royal College of Psychiatrists. "A very good psychologist or psychiatrist who spends in-depth time with him would be able to pick up (a problem), but you have to throw an awful lot of resources at it to do that and often, I don't think (pilots) are getting in-depth assessments," Persaud said.

Annual medical checkups

The president of the German pilots union Cockpit said medical checkups are done by certified doctors and take place once a year.

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People pay their respects at a memorial for the victims in the village of Le Vernet, near the crash site, on Friday. (Robert Pratta/Reuters)

"At the moment all the evidence points clearly in one direction and it's the most likely scenario, there's no doubt about that," Ilja Schulz told The Associated Press. "But all the pieces must be put together to see whether there were any other factors that played a role, or not. Only then can you draw lessons that will improve security in future."

French investigators, who are in charge of the probe into the plane crash, believe the 27-year-old locked himself inside the cockpit and then intentionally smashed the Germanwings plane into a mountainside during a flight from Barcelona to Duesseldorf.

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."

Human remains retrieved

In Vernet, the village close to the crash site, flowers began to accumulate at a memorial for victims.

French police said recovery workers continue to find human remains from the flight, but have recovered no intact bodies.

Speaking from the French Alps town of Seyne-les-Alpes, Col. Patrick Touron of the gendarme service said DNA samples have been taken from objects provided by the victims' families, such as toothbrushes, that could help identify the victims. Touron also said jewelry and other objects could help in the identification process.

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 CEO Thomas Winkelmann said in a statement.

French Prime Minister Manuel Valls on Friday called on Lufthansa to provide all information it has about Lubitz "so that we can understand why this pilot got to the point of this horrific" action.

Pilots' union angry over media leaks

France's leading pilots' union is filing a lawsuit over leaks about the investigation into the crash.

Guillaume Schmid, a representative of the SNPL union, said Friday that pilots are angry that information about the dramatic final moments of the flight were reported in the media before prosecutors and others were informed.

After the media reports, a prosecutor announced that cockpit recordings indicate the co-pilot of the jet intentionally flew the plane into a mountain.

The lawsuit is over violating a French law on keeping information about investigations secret while they are ongoing. The lawsuit doesn't name an alleged perpetrator, a common method in French law that leaves it to investigators to determine who is at fault.

Schmid said pilots are saddened by the accident and understand the public's wish for immediate information, but decried pressure on investigators and said that can lead to misleading the public instead.

James Phillips, a pilot and international affairs director of the German Pilots Association, cautioned against drawing conclusions at such an early stage in the investigation.

Support lines available for health issues

"[Lubitz] may be at fault, but we don't know," he told CBC News on Friday.

The only way to make aviation travel safer is to "get all the information before we make the judgment," he said. "It's all happening very, very fast."

German co-pilot's hometown reacts to crash1:47

"We do have support lines for pilots that they can call on private issues," Phillips said. "Most of the airlines that we work with have them as well, to try to make sure that the pilots don't [work] if they're concerned with health issues, if they are concerned about any issues.

"I accessed it when my mother passed away. I called and said, 'I'm not fit to be in the cockpit because I am concentrating on my mother,' and my airline said, take two weeks off. Call us when you feel better."

"And I think this should actually be the real way to go forward, but I realize it's based on a trust and honesty situation, which sometimes is very difficult."

With files CBC News and Reuters