They have not yet found the flight data recorder, but they have released the cockpit voice recorder (CVR), and it appears that one of the pilots was locked out of the cockpit:

As officials struggled Wednesday to explain why a jet with 150 people on board crashed amid a relatively clear sky, an investigator said evidence from a cockpit voice recorder indicated one pilot left the cockpit before the plane’s descent and was unable to get back in.

A senior military official involved in the investigation described “very smooth, very cool” conversation between the pilots during the early part of the flight from Barcelona, Spain, to Düsseldorf, Germany. Then the audio indicated that one of the pilots left the cockpit and could not re-enter.

“The guy outside is knocking lightly on the door, and there is no answer,” the investigator said. “And then he hits the door stronger, and no answer. There is never an answer.”

He said, “You can hear he is trying to smash the door down.”

While the audio seemed to give some insight into the circumstances leading to the Germanwings crash on Tuesday morning, it also left many questions unanswered.

It’s now beginning to sound like deliberate action by one of the pilots, though it’s curious that the descent was not steeper.