Germanwings flight: Investigators find evidence that pilot was not fit to fly.

Evidence has been found that sheds light on why the pilot may have deliberately downed the plane.

READ MORE: He ‘deliberately crashed’ flight 9525. But who was Germanwings co-pilot Andreas Lubitz?

The co-pilot believed to have deliberately crashed a Germanwings plane into the French Alps had hidden an unspecified medical condition from his employer and had torn up recent documents in his home saying he was unable to work, German state prosecutors say.

One hundred and fifty people, including a Victorian woman and her adult son, died when the plane slammed into the mountainside on Tuesday.

A French prosecutor said Andreas Lubitz, 28, deliberately crashed the Airbus A320, with the senior pilot locked out of the cockpit.

After listening to the cockpit voice recorders, prosecutors in France offered no motive for why Lubitz would take the controls of the plane, lock the captain out and deliberately set it to veer down from its cruising altitude at a rate of 3,000 feet per minute.

RELATED: Germanwings crash: Co-pilot Andreas Lubitz’s intention “was to destroy the plane.”

German investigators carried out searches in the homes of the Lubitz, seizing documents and a computer.

“Documents with medical contents were confiscated that point towards an existing illness and corresponding treatment by doctors,” the prosecutors’ office in Duesseldorf said.

“The fact there are sick notes saying he was unable to work, among other things, that were found torn up, which were recent and even from the day of the crime, support the assumption based on the preliminary examination that the deceased hid his illness from his employer and his professional colleagues.”

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

The documents were found in searches of Lubitz’s apartment in Duesseldorf and his parents’ home in the town of Montabaur.

The German prosecutor’s office said the searches found no sign of political or religious motives, and no suicide note was found.

The office said it would take some days to evaluate the documents seized.

A Dusseldorf university clinic said Lubitz had attended for diagnosis earlier this year, but said media reports that he was treated at the facility for depression were wrong.

The could not give further details because of privacy rules.

Co-pilot suffered ‘depressive episode’ six years ago: reports

Earlier, German tabloid newspaper Bild reported the co-pilot received psychiatric treatment for a “serious depressive episode” six years ago.

READ MORE: This is what depression feels like. (From someone who’s lived it).

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

The chief of Lufthansa, which runs the low-cost Germanwings airline, Carsten Spohr told a news conference on Thursday that Lubitz had taken a break during his training six years ago, but did not explain why.

He said Lubitz passed all tests to be fit to fly.

“Six years ago there was a lengthy interruption in his training,” Mr Spohr said.

“After he was cleared again, he resumed training.

“He passed all the subsequent tests and checks with flying colours. His flying abilities were flawless.”

A Lufthansa spokeswoman said on Friday the airline would not comment on the state of health of the pilot.

Captain used axe in attempt to bash down door: report

The Bild newspaper also reported the captain who was locked out of the cockpit used an axe to try and force his way back in, citing security sources.

The cockpit flight recorder showed the captain repeatedly knocked and tried to get back in as the plane went into its fatal descent, French prosecutors said.

However, Bild reported that the captain also tried using an axe to break down the cockpit’s armoured door.

This could not be immediately confirmed, but a spokesman for Germanwings confirmed to news agency AFP that an axe was on board the aircraft.

Such a tool is “part of the safety equipment of an A320”, a spokesman said.

Federal Government, Qantas considering cockpit safety changes

The Federal Government and Qantas are considering changes to cockpit security following the crash.

Deputy Prime Minister Warren Truss said Australia’s aviation agencies were investigating if current cockpit safety requirements needed further strengthening.

RELATED: For everyone who is feeling scared about getting on a plane today.

“The current regulations do not require airlines to replace a pilot who temporarily leaves the cockpit,” he said.

“Careful consideration needs to be made following thorough investigation to ensure that altering current procedures does not open other potential vulnerabilities.”

“Our two major international and domestic airlines are undertaking their own safety and security risk assessments of cockpit procedures following the recent tragedy.”

A Qantas spokesman said the airline was “monitoring the information coming out of the French investigation” and was considering whether any changes to its existing safeguards were needed.

Strategic Aviation Solutions chairman Neil Hansford told ABC NewsRadio there had been several similar incidents in the past.

“We didn’t have these doors on cockpits to keep them sanitary before 9/11 so this is another flow-on effect,” he said.

Airlines including Norwegian Air Shuttle, Britain’s easyJet, Air Canada, Air New Zealand and Air Berlin all said they had introduced a requirement that two crew members must be in the cockpit at all times.

Regulations in the US already require that no pilot must ever be left alone at the controls and Canada has now followed suit.

Lufthansa said on Thursday that it did not see any reason to change its procedures, but later announced it would adopt new rules requiring two crew members to be in the cockpit at all times.

“The passenger airlines of the Lufthansa Group will put this new rule into place as soon as possible in agreement with the relevant authorities,” Lufthansa said in a statement on Friday.

This story first appeared on ABC Online and is republished here with full permission.