Germanwings audio retrieved but no clues on why plane crashed

French investigators retrieved a smashed black box and extracted audio from its cockpit voice recorde, but found no explanation for why the Germanwings airbus 320 dropped unexpectedly and smashed into a rugged Alpine mountain, killing 144 passengers and six crew members.

The orange cockpit voice recorder is considered the key to knowing why the pilots lost radio contact with air traffic controllers over the French Alps then crashed Tuesday during a routine flight from Barcelona to Duesseldorf.

A top German security official said there was no evidence of foul play while French official said terrorism appeared unlikely.

The retrieval of the audio file is crucial, but it is too early to draw any conclusions, the French aviation investigative agency said. The recorder

audio feeds from four microphones in the cockpit and records all the conversations between the pilots, air traffic controllers as well as any noises.

The plane, operated by Germanwings, a budget subsidiary of Lufthansa, was less than an hour from landing in Duesseldorf when it unexpectedly went into a rapid, eight-minute descent. The pilots sent out no distress call, France’s aviation authority said.

A former air safety investigator with the National Transportation Safety Board told AP that the four possible causes of any crash are human error, mechanical problems, weather, criminal activity or a combination of two or more.

From what has emerged so far, it was established that the airbus hurtled downward from relatively clear skies above the French Alps for about 10 minutes.

The rate of descent from its cruising altitude of 38,000 feet was alarming but still gradual enough to indicate that the twin-engine plane had not suffered any catastrophic damage and might have remained under the control of the pilots or the autopilot. 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 behind almost no apparent clues about what caused the crash.