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LONDON, Dec. 7 (Xinhua) -- The helicopter crash which claimed the lives of Leicester City owner Vichai Srivaddhanaprabha and four other people was almost certainly caused by a mechanical fault in the rotor system in the helicopter's tail, according to preliminary findings of the investigation into the accident.

The crash happened moments after the helicopter had taken off from Leicester's King Power Stadium following a Premier League game against West Ham on October 27th.

Images of the crash show the helicopter taking off before losing control and spinning into a car park outside the ground, killing everyone on board.

The Air Accident Investigation Branch (AAIB), who published the report, confirmed they had focused their investigations on a mechanical failure in the tail rotor.

The report found that "evidence gathered shows that the loss of control of the helicopter resulted from the tail rotator actuator control shaft becoming disconnected from the actuator lever mechanism."

"Also, the pin and one of the locating bearings were missing from the lever and the locking nut and pin carrier were found loose in the tail rotator and were bonded together - they should be separate."

The report adds that there was no grease in the debris, "which in a hydraulic system is crucial," and this would have led to the pilot losing control of the craft, causing it to go into the fatal spin.

The investigation continues.