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.

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.

The report is based on the bureau's initial assessment and findings gathered in the early phase of the investigation, and it will be released to the public later this week.