Germanwings plane crash: Investigators may have already found remains of suspected killer co-pilot Andreas Lubitz

Reports suggest Lubitz may have been suffering from a detached retina when he 'deliberately' crashed the Airbus A320 into the French Alps

Searchers work to collect debris and find the second black box at the crash site of the Germanwings Airbus A320 in the French Alps, 29 March 2015 (EPA)

Forensic teams working on the site of the Germanwings crash may already have recovered the body of suspected killer co-pilot Andreas Lubitz, as it emerged that a road is being built to the remote location in the French Alps.

Investigators say tests on Lubitz’s body could provide crucial clues to explain why he might have locked himself in the cockpit of Flight 9525 and set the plane’s autopilot to crash into the side of a mountain.

Speaking to Germany’s Bild newspaper, leading forensic scientist Professor Michael Tsokos said his team had been working round the clock to test and sort as many as 600 separate body parts from the 150 people killed in the crash.

Mr Tsokos said he hoped that within three weeks up to 95 per cent of all the victims will have been identified and officially declared dead, and was reported as saying Lubitz’s body was among those already recovered.

But while Marseille prosecutor Brice Robin said that 78 distinct DNA strands had been isolated among the remains, he refused to confirm that any of the remains had been formally identified.

German media carried reports on Sunday that Lubitz may have been suffering from a detached retina, and officials have said it appears he was hiding details of an unspecified medical condition from his employers.

And while the pilot was also reported as having a history of depression, Robin said police were yet to speak to his family “out of decency and respect for their pain”.

Mr Robin told the AFP News Agency that investigators still haven’t found the second “black box” flight recorder at the crash site, which monitors technical data and could allow them to definitively rule out any mechanical failure with the plane.

He said that authorities were building a road to allow access for all-terrain vehicles to the site in the mountains above the village of Prads-Haute-Bléone. It will make it easier to remove largest parts of the plane – though they are no bigger than a car – and could be completed by Monday night, Robin said.