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.

While no mechanical or design fault has been identified with the GE Aerospace GEnx-1B engines or the switches themselves, experts confirmed that the post-crash analysis showed no fuel contamination or flap retraction issues – commonly suspected in such events.

The much-awaited preliminary report on the devastating Air India crash, involving a Boeing Co. BA +1.68% Get Free Report airplane, in June, which claimed 260 lives, is expected to be released by the end of this week.