Trace amounts of alcohol were found in blood samples taken from the dead captain of a Boeing 737 passenger jet that crashed in central Russia last September, according to the Interstate Aviation Committee.

It is now thought that alcohol may have triggered fatigue and a loss of orientation in the pilot. Further, a lack of professional training has been pointed out by investigators. These conclusions follow studies of the flight data recorder taken from the wreckage of the aircraft.

Also, investigators have not ruled out the responsibility of air traffic control staff in the air disaster.

All 88 people onboard, including six crew members, died when the plane came down on September 14, 2008, in the city of Perm.

Earlier, Russian newspapers blamed the pilots for the crash, suggesting they misjudged the situation because they didn't have enough experience flying a 737. One of the pilots had spent most of his flying career in a Tu-134, while the other was an experienced AN-24 pilot.