Eurocopter confirmed yesterday it had identified a problem with the fuel indication and alert system on some EC 135 models.
It comes two weeks after the Police Scotland helicopter, a Eurocopter EC 135, crashed into the roof of the city bar, initially claiming nine lives, including the pilot and two others on board. A 10th victim died of his injuries last week.
The company's technicians have been carrying out safety checks since Bond Air Services discovered the fault last Wednesday on its North West Air Ambulance in England. The operator immediately suspended flights on all 22 of its EC 135s, but many have since been given the all-clear to resume flights.
In an urgent safety notice, Eurocopter has raised concerns of the possibility of the aircraft's instruments giving inaccurate fuel readings.
The statement read: "Eurocopter has been informed by Bond of an issue involving the fuel indication system on one of its EC135 EMS aircraft during normal operation.
"Following this incident, tests performed on EC 135 have revealed supply-tank fuel gauging errors on some aircraft. The first analysis shows the indication of the fuel quantity in the supply tanks could be overestimated."
The warning was not the first Eurocopter had issued regarding the EC 135, having previously released a notice highlighting the "possible water contamination of the fuel system".
In response to the manufacturer's statement, Bond said: "We understand other operators have since conducted similar tests and found similar problems with their aircraft.
"As soon as we discovered this issue, in line with our commitment to the highest standards of safety, we took the prudent decision to temporarily suspend service operations while it conducted checks on our fleet of EC 135s.
"The results of these tests were subsequently validated by Eurocopter, and appropriate repairs made before returning the aircraft to service."
Bond demanded all EC 135s should have a minimum of 90kg of fuel onboard.
The Air Accidents Investigation Branch (AAIB), which is investigating the Clutha tragedy, said it will not provide a "running commentary".
However, in its preliminary report, it found that neither the main rotors or tail rotors were rotating at the moment of impact.
It also stated the Police Scotland helicopter had about 95 litres of fuel when it crashed.
Recent claims have suggested pilot error may have been one of the causes of the disaster.
Sources close to the investigation say the AAIB does not believe the accident was the result of a mechanical fault.
Unsourced weekend reports suggesting pilot David Traill mishandled an unexpected "technical event" have not been confirmed.
Meanwhile, a legal helpline has been set up by the Scottish Trades Union Congress on 08000 89 19 198 for the victims and families of those caught up in the Clutha tragedy.