The co-pilot of the Germanwings flight that crashed into the French Alps took sole control of plane and intentionally started the descent, officials say, reports the BBC.

CNN reports that from what investigators have found, it seems the co-pilot "wanted to destroy the aircraft," prosecutor says of the Germanwings crash, say.

French prosecutors, citing information from the cockpit voice recorder said the pilot had just left the cockpit and had been unable to re-enter it.

Evidence from a cockpit voice recorder, retrieved from the crash site in the French Alps, indicated that one pilot left the cockpit before the plane's descent and was unable to get back inside, The New York Times reports.  

"The guy outside is knocking lightly on the door and there is no answer," The New York Times quoted an unidentified investigator. "And then he hits the door stronger and no answer. There is never an answer."

"You can hear he is trying to smash the door down," the investigator added. 

However, the investigator said that they were unaware why the pilot left the cockpit. "But what is sure is that at the very end of the flight, the other pilot is alone and does not open the door," he told NYT.