Dave Miller, deputy chief inspector of the Air Accidents Investigation Branch (AAIB), said there was no mayday call, no explosion and no fire before the Police Scotland helicopter made a "vertical descent" onto the roof of the Clutha pub in Glasgow, causing debris to collapse on revellers below.
Police last night confirmed that the search and recovery operation at the site had concluded, with officials satisfied there are no further fatalities at the scene. Nine bodies had already been recovered from the scene.
As the AAIB said its preliminary report would be published very soon, it was confirmed that nothing fell from the craft before the accident, and that the helicopter rotors were intact at the moment of impact.
Mr Miller said: "We have recorded radio information and transmissions and I can confirm that there were no emergency transmissions from the pilot before this accident." He also indicated there were hopes of recovering data due to the "significant number of modern electronic systems onboard".
The AAIB said that while the police helicopter was built by Eurocopter, the company whose Super Puma range of helicopters have been involved in fatal accidents in the North Sea, there was "no cause to connect" the Glasgow crash with those incidents.
Air accident investigators will, however, take into account the history of the Eurocopter EC 135 involved in Friday night's crash, with the latest incident the third time in three years there has been safety concerns.
Last year Scotland's two EC 135 air ambulance helicopters were grounded by operator Bond Air Services for a time following reports of cracks in the rotor blades on some of the aircraft. It was the first time safety concerns had led ambulance bosses to suspend flights in the 12 years since they began operating in Scotland.
Yesterday the bodies of the final four victims which remained trapped inside the Clydeside venue were removed after the extensively damaged Eurocopter craft was lifted out by crane.
The wreckage of the three-tonne aircraft was removed from the building in a painstaking operation which allowed emergency services to search the area inside the bar.
Emergency service workers formed a guard of honour to pay their respects to the victims as their bodies were driven away in private ambulances.
The crash site is subject to an ongoing police investigation but management of the incident scene has now been handed to Glasgow City Council.
Pope Francis sent a message expressing his "closeness" to the people of Glasgow following the tragedy.
The three helicopter crew died in the incident, along with six people inside the pub. Five victims have been formally identified. Samuel McGhee, 56, of Glasgow, and 48-year-old Gary Arthur, from Paisley, Renfrewshire, had both been inside the pub. The three dead helicopter crew were pilot David Traill, 51, and police constables Kirsty Nelis, 36, and Tony Collins, 43.
John McGarrigle, 59, from Castlemilk, and Mark O'Prey were also believed to have been inside the pub.
Police said last night that 11 of the 32 people who were injured in the crash were still in hospital.
Last year's grounding of Scotland's two air ambulance helicopters came weeks after the European Aviation Safety Agency (Easa) ordered daily safety inspections to be carried out on the EC 135 helicopters after a crack was found on the main rotor of a Scottish air ambulance during a routine inspection. In October 2010, Easa also ordered a worldwide inspection of all 1000 helicopters of the same model, warning part of the transmission to the main rotor was not up to standard.
A previous report by Easa highlighted how an engineering and laboratory investigation had found that deformed safety pins used to secure blade bolts could have caused them to rotate. The report said the flaw "could lead to further crack propagation, possibly resulting in main rotor hub failure and consequent loss of the helicopter".
An AAIB spokesman said of the EC 135's history: "We cannot rule things in or out at this stage, but we would be looking at this."
Bond Air Services, the operator of the Police Scotland helicopter, said it had no plans to stop using the EC 135 aircraft.
Eurocopter, the French subsidiary of EADS the European aerospace company, said there was no evidence so far to warrant grounding.
A spokesman for the British Airline Pilots Association said: "We are not calling for the aircraft type to be grounded at this stage but would support the AAIB if that was its recommendation."
Meanwhile a 16-year-old boy was arrested for allegedly posting sectarian and racist comments on Twitter in the wake of the crash. He is expected to appear at Ayr Sheriff Court later.