Experts have raised questions about information not included in the preliminary report, writes the BBC's Theo Leggett.

A preliminary report released by India’s Aircraft Accident Investigation Bureau a month after the fatal June 12 Air India crash has not yet provided a conclusive assessment as to why the tragedy occurred – and speculation has run rife in the absence of answers.

An Air India executive is still urging its staff not to jump to any conclusions as the investigation into the crash that killed 260 people last month continues. A preliminary report into the June crash found that the plane's fuel control switches had been flipped off one by one.