The Transport Accident Investigation Commission says the heli-skiing flight was coming in to land when it crashed on Saturday.
The smash resulted in the death of Auckland construction company owner Jerome Box (52) and injured six others on board, including members of his church.
Priest leader Mathew Newton yesterday told churchgoers at Auckland's St Paul's, packed with hundreds of people - including some openly weeping - to prepare for ''a tough couple of weeks''.
''[Jerome] died and a number of others were quite badly injured, and it's actually a miracle they walked away from that incident.''
Mr Newton invited the partners of people on the trip to come to the front of the church and lead prayers. He later said there was a ''sense of guilt around being a survivor''.
The Skyline Enterprises-owned, Harris Mountains Heliski Squirrel helicopter crashed into Mount Alta, about 25km northwest of Wanaka, about 12.20pm on Saturday, spreading wreckage over about a kilometre in steep, snow-covered terrain at high altitude.
''The aircraft has rolled into a small ravine, so the wreckage is over quite a significant area with some challenges with the access,'' TAIC lead investigator Ian McClelland told media at Queenstown Airport yesterday.''
The preliminary information we have is the aircraft was in the process of landing.
''Harris Mountains Heli-Ski boss Mark Quickfall told the Otago Daily Times yesterday the alarm was raised by a heli-ski guide who saw the crash ''from a distance''.
''One of the guides, not on the helicopter, but skiing in the vicinity actually spotted the helicopter going in to land and obviously have an accident.''
The guide called the heli-ski base, sparking a rescue effort involving a large number of helicopters, paramedics, ski guides trained in first aid, police and alpine search and rescue crews.
A stream of helicopters carried those injured to the Lake Wanaka Medical Centre and four were then transferred to Dunedin Hospital.
All except guide Mark Sedon have since been discharged and have returned to their homes in Auckland and Queenstown.
Two TAIC investigators, who arrived in Wanaka yesterday morning, flew over the crash site. It is believed they landed on the side of the mountain for a closer look. A more thorough examination, with the head investigator present, will take place on Mount Alta today.
''It is a challenging environment, in terms of the terrain and also the weather at the moment, and so we're seeking some expert advice before we do venture on to the slopes,'' Mr McClelland said.
Civil Aviation Authority spokesman Mike Richards said on Saturday he understood the helicopter ''clipped'' the mountain but Mr McClelland steered clear of any possible causes.
''That's rumour at this stage. Our objective at this stage is just to gather all the information and then we'll do the analysis later on.''
He said today's priority was for the three TAIC investigators to have a full day examining the crash site. Interviews of the pilot and surviving passengers would follow, dependent on their health and availability.
The wreckage would be recovered after the scene examination was completed.
The investigation could take up to 18 months, he said, and would aim to identify all contributing factors and safety issues to ensure such a crash did not happen again.
The helicopter was piloted by Dave Matthews, of Queenstown, who joined the Helicopter Line in 2008 and had flown for three or four seasons of heli-skiing.
Yesterday afternoon Mr Matthews was heading home from Dunedin and Mr Quickfall had yet to speak to him.
Asked about the general hazards encountered by heli-ski pilots, Mr Quickfall said wind was one factor and ''flat light'', which made visibility difficult, was another.
''But that wasn't the case [on Saturday] ... there weren't strong winds and there certainly wasn't flat light.
''But it would only be speculating to suggest what might have gone wrong.''
The ill-fated trip into the mountains was the third or fourth of the day for Mr Matthews on Saturday and the second for the Auckland heli-skiers.
Skiers are normally unloaded at new drop-off points for each run, so they have ''untouched snow'' in front of them.
Skyline Enterprises owns both the Helicopter Line and the heli-ski business.
Additional reporting by APNZ.
