A preliminary report into the deadly crash of an Air India jetliner in June is expected to be released by Friday, three sources with knowledge of the matter said, with one adding the probe had narrowed its focus to the movement of the plane's fuel control switches.

As the 30-day limit to submit the report of the preliminary investigation into the June 12 Air India accident in Ahmedabad to the Internationa.

The investigation into the Air India flight 171 crash is focusing on the movement of the engine fuel control switches, following an analysis of the Boeing 787's flight and voice data recorders