Indonesia's top accident investigator says there are no indications of foul play in last month's crash of an AirAsia jetliner with 162 people on board.

National Transportation Safety Committee head Tatang Kurniadi said Wednesday that an analysis of the Airbus A320's cockpit voice recorder shows no signs of sabotage or terrorism.

AirAsia Flight 8501 crashed into the Java Sea on Dec. 28 shortly after the pilots asked to climb from 32,000 feet to 38,000 feet to avoid threatening clouds, but were denied permission because of heavy air traffic. No distress signal was received.

Kurniadi told reporters that the contents of the plane's two "black boxes" have been downloaded and are being analyzed together with advisers from Airbus, the plane's manufacturer. He said a preliminary report is expected next week.