Germanwings Flight 9525 co-pilot Andreas Lubitz is suspected to have crashed the plane because he “feared that his medical problems would endanger his fitness to fly,” CNN reported Tuesday, citing German newspaper Bild. The 27-year-old had been treated for suicidal tendencies years before last week’s crash, German prosecutors said Monday.

Bild reported, citing an unnamed investigator, that one of the main motives behind the co-pilot’s action could be that he was afraid his medical conditions would jeopardize his career. Lubitz had previously seen psychotherapists "over a long period of time" due to "suicidal tendencies," which occurred before he received his pilot’s license in 2013. However, Christoph Kumpa, a spokesman for the prosecutor, said that there was no evidence suggesting that Lubitz was suicidal or had been acting aggressively before last Tuesday's crash.

Investigators, who are trying to determine why Lubitz might have intentionally caused the crash, have not found any suicide note from Lubitz’s apartment in Dusseldorf or his parents' house in Montabaur. Prosecutors have alleged that Lubitz deliberately crashed Flight 9525 in the French Alps, killing all 150 people, including himself, on board. He reportedly locked Captain Patrick Sondenheimer out of the cockpit as he initiated the plane's descent.

A transcript of the Airbus A320’s cockpit voice recorder, published by Bild, revealed Sondenheimer shouting, "Open the goddamn door," as he tried to break into the locked cockpit. A conversation between the captain and Lubitz -- shortly after the flight took off from Barcelona for Dusseldorf -- indicated that Lubitz had encouraged Sondenheimer to use the toilet.

Meanwhile, recovery workers are looking for the remains of those killed in the crash. Authorities told CNN on Tuesday that an access road to the crash site has been completed, and the road, linking Le Vernet, a nearby community, to the crash site, will reportedly reduce the time it takes to reach the wreckage. The DNA of 78 victims has so far been isolated, and authorities are optimistic that the remains of the rest of the victims will soon be found and identified, according to reports.