Story highlights Investigators hear "no threats" in the contents of the cockpit voice recorder, official says

It's still unclear what brought down Flight QZ8501 with 162 people on board last month

(CNN) Audio recordings from the cockpit of AirAsia Flight QZ8501 contain no sounds of gunfire or explosions, making it unlikely the plane was brought down by terrorism, Indonesian investigators say.

The aircraft's cockpit voice recorder, which captures all noises on the flight deck, was recovered last week from the depths of the Java Sea, along with the other so-called black box, the flight data recorder.

"The voice from the cockpit does not show any sign of a terrorist attack. It is only the pilot, sounding very busy," Andreas Hananto, an investigator at Indonesia's National Transportation Safety Committee, said in an interview with the news agency Reuters.

He said Monday that investigators had heard "no threats" in the recordings.

"We didn't hear any voice of other persons other than the pilots," Nurcahyo Utomo, another investigator, told Reuters.

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