An official report on the world’s deadliest aviation accident in a decade, seen by CNN, has answered one key question – but raised others.

The granddaughter of a victim of the Air India Flight 171 crash has said a preliminary report into the incident was "incomplete" and that she "can't be at peace" without those responsible being held accountable.

The Air India airliner carrying 230 passengers and 12 crew members was on its way to the United Kingdom when it crashed into a building shortly after takeoff on June 12, killing all aboard, except for one survivor, and several people on the ground, according to authorities.