Indonesian investigators say it is unlikely an explosion caused the AirAsia jet to crash in Java Sea last month.
A total of 162 people died when the plane came down on 28 December, less than half way into the two-hour flight between the Indonesian city of Surabaya and Singapore.
And investigators say they have ruled out terrorism after listening to cockpit voice recordings.
Nurcahyo Utomo, from the National Transportation Safety Committee, said: “We didn’t hear any sounds of gunfire or explosions. For the time being … we can eliminate the possibility of terrorism.
“We didn’t hear any voice of other persons other than the pilots.”
Another investigator, Andreas Hananto, said they found no evidence of “threats” being made on board the Airbus A320-200.
“The recording indicates that the pilot was busy with the handling of the plane,” he said.
“It’s unlikely there was an explosion … If there was, we would definitely know because certain parameters would show it.”
Last week, an official from the National Search and Rescue Agency had suggested pressure could have caused the airliner to explode when it hit the sea.
Indonesian authorities believe bad weather could be to blame for the disaster.
Investigators from Indonesia, France, Singapore and China have listened to the whole cockpit voice recording, but only transcribed half of it. They hope to finish transcribing it by the end of the week.
They have refused to give more details about the final moments of the flight, which crashed around 40 minutes after take off.
Analysis of the second black box – the flight data recorder — is expected to take longer because the aircraft’s previous 72 flights will also be examined.
A preliminary report into the crash is expected to be published next week, but it is thought the full report will take up to a year and will not include the entire cockpit voice transcript.