The German aviation authority did not know about co-pilot Andreas Lubitz's medical background prior to the Germanwings crash that killed 150 people, it told Reuters on Sunday, raising more questions over medical oversight of pilots.

Lubitz, believed to have deliberately steered the plane into a mountain in the French Alps, broke off his pilot training for several months in 2009 and upon restarting informed the Lufthansa pilot training school by email he had overcome a period of severe depression.

Lufthansa, the parent company of Germanwings, has said he passed all medical and suitability tests upon restarting training.