Investigators have found no initial evidence of engine or gearbox failure in their inquiry into the police helicopter crash in Glasgow that claimed nine lives.

In a special bulletin, the Air Accidents Investigation Branch (AAIB) said "all significant components were present" at the time of the crash.

The two-engine Eurocopter EC135 helicopter crashed through the roof of The Clutha Bar on 29 November.

The AAIB said: "Initial assessment provided no evidence of major mechanical disruption of either engine.

"[It] indicated that the main rotor gearbox was capable of providing drive from the No 2 engine turbine to the main rotor and to the fenestron drive shaft."

The pilot of the helicopter, David Traill, 51, and his two passengers, police officers Kirsty Nelis, 36, and Tony Collins, 43, were killed in the crash, as were six people inside the pub.

The AAIB said the helicopter had left Glasgow City Heliport at 8.45pm on the Friday of the crash.

It said the helicopter had initially flown to a location on the south side of Glasgow city centre. It stayed there for about 30 minutes.

The helicopter then flew to Dalkeith in Midlothian, staying there for a further ten minutes before returning to Glasgow.

At 10.18pm, the pilot had requested clearance from air traffic controllers to re-enter the Glasgow control zone and return to the heliport.

This had been approved and no further radio transmissions were received from the pilot.

The AAIB said radar contact with the helicopter was lost at 10.22pm.

The report went on: "Around this time, the helicopter was seen and heard by a witness who described hearing a noise like a loud 'misfiring car', followed by silence.

"He then saw the helicopter descend rapidly. It crashed through the roof of The Clutha Bar, a single-storey building on Stockwell Street in central Glasgow."