A preliminary report on the investigation into the Air India flight that crashed last month has answered some questions about the fatal accident but raised many more and fuelled speculation about the cause.

India's aircraft accident investigation body said on Thursday it was too early to reach any "definite conclusions" on what led to the deadly Air India Boeing plane crash last month that killed 260 people.

An investigation into the Air India Dreamliner that crashed last month and left 260 people dead has revealed a mysterious audio recording.