A section of the preliminary report into the Clutha crash in November 2013 had argued the disaster could have been due to mechanical failures, not pilot error.

The document, which did not feature in the final version of the investigation report, has highlighted the possibility of technical issues playing its part in the tragedy.

Earlier this year, it had been suggested that pilot David Traill had ignored a low fuel signal, which may have contributed to the helicopter coming down on the Glasgow pub, claiming 10 lives.

However, it is said that a fault in the aircraft’s fuel system may have provided the pilot with conflicting information.

A preliminary report from the Air Accident Investigation Branch found contributory factors such as a leak of water and washing fluid into the fuel tank.

As a result, the pilot may have been given an unreliable fuel reading and therefore thought he had more time in the air.

The initial report was sent to Police Scotland along with operators Bond Air Services and manufacturers Airbus Helicopters.

In their official report, crash investigators said the pilot turned off fuel pumps and ignored low fuel warnings.

However, the earlier dossier said that a “fuel caution” light “may not have illuminated”.

This is different to the “low fuel” warning which measures fuel supply in a different way.

Manufacturers Airbus Helicopters refused to discuss the information, while Police Scotland declined to comment.