This story has been updated to add confirmation from a German official that only one of the plane's two pilots was in the cockpit at the time of the crash.

After a New York Times report claimed, citing an investigator, that one of the pilots of Germanwings Flight 9525 had been locked out of the cockpit in the final moments before the crash, several reports have emerged debating the possibility of such an event and whether an Airbus A320's cockpit can indeed be locked from the inside.

According to the Associated Press (AP), an Australian pilot who flew Airbus A320 planes for six years claimed that it is possible to lock the plane's cockpit door from the inside despite the presence of an access keypad on the outside that allows entry in the event of an emergency. The reports followed comments to the Times by a senior military official with access to Flight 9525's cockpit voice recordings. The official had claimed Wednesday that one of the two pilots appeared to have been locked outside the cockpit while the plane descended rapidly before crashing into a mountainside in the French Alps on Tuesday. The Airbus A320 was flying from Barcelona to Dusseldorf with 150 people on board.

Christoph Kumpa, a German state prosecutor on Thursday confirmed that only one of the two pilots was in the cockpit when Flight 9525 crashed on Tuesday, Reuters reported, adding that the information came from French investigators. However, Kumpa reportedly said that it was unclear if it was the captain or the co-pilot who was in the cockpit.

A video posted by flight-tracking site Flightradar24 shows the normal and emergency procedures to access an Airbus A320 cockpit. According to the video, staff can use an emergency code to access the cockpit in case both pilots become incapacitated. The video shows that staff can enter a code that triggers a timer for 30 seconds, following which a buzzer in the cockpit sounds continuously. If there is no response from the cockpit crew in that time span, the door is unlocked for five seconds. However, according to the A320 pilot, who was not named, if the person in the cockpit denies access during the emergency unlocking procedure, the door stays locked, AP reported.

Lufthansa, which owns the German low-cost airline, said that the co-pilot had worked for Germanwings since September 2013, directly after finishing training, and had flown a total of 630 hours for the airline. The captain had more than 6,000 hours of flying time. The identities of the two pilots are yet to be revealed.

All 150 people on board are feared dead, and investigators are analyzing data from the plane's black boxes to determine the cause of the crash. Authorities said that both devices have been badly damaged and the memory card of the flight data recorder is missing. However, they have been able to recover an audio file from the cockpit voice recorder, reports said. 

Here is the Flightradar24 video showing the procedure to access an Airbus A320 cockpit.