International

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.We don’t know yet the reason why one of the guys went out,” said the official, who requested anonymity because the investigation was continuing. “But what is sure is that at the very end of the flight, the other pilot is alone and does not open the door.”

The data from the voice recorder seems only to deepen the mystery surrounding the crash and provides no indication of the condition or activity of the pilot who remained in the cockpit. The descent from 38,000 feet over about 10 minutes was alarming but still gradual enough to indicate that the twin-engine Airbus A320 had not been damaged catastrophically. At no point during the descent was there any communication from the cockpit to air traffic controllers or any other signal of an emergency.

When the plane plowed into craggy mountains northeast of Nice, it was traveling with enough speed that it was all but pulverized, killing the 144 passengers and crew of six and leaving few clues.

The French aviation authorities have made public very little, officially, about the nature of the information that has been recovered from the audio recording, and it was not clear whether it was complete. France’s Bureau of Investigations and Analyses confirmed only that human voices and other cockpit sounds had been detected and would be subjected to detailed analysis.

Asked about the new evidence revealed in the cockpit recordings, Martine del Bono, a bureau spokeswoman, declined to comment. “Our teams continue to work on analyzing the CVR,” she said, referring to the cockpit voice recorder. “As soon as we have accurate information we intend to hold a press conference.”

Meanwhile, prosecutors in Marseille, who have been tasked with a separate criminal inquiry into the crash, could not immediately be reached for comment. Brice Robin, the Marseille prosecutor, was due to meet Thursday morning with the families of the crash victims.

At the crash site, a senior official working on the investigation said, workers found the casing of the plane’s other so-called black box, the flight data recorder, but the memory card containing data on the plane’s altitude, speed, location and condition was not inside, apparently having been thrown loose or destroyed by the impact.