Frye (18) fell from the Steven Woodsford-trained Zuleika about 150m in to the 1200m when the 3yr-old filly faltered and fell.
''It was awkward away, and you can see Ashley obviously had concern with it because it wasn't stretching out,'' co-chief stipendiary steward Nigel McIntyre said.
''From there, it's gone 150m and collapsed to the track at a considerable distance off the back of the field and clear of other horses.
''[Frye] has made a heavy impact on the ground with her head.''
McIntyre said an autopsy of Zuleika, who was put down after breaking a near hind leg and sustaining a fracture around the hip area, revealed the horse had suffered a severe rupture to an artery.
''It's filled up with blood and crashed to the track step-by-step and broken its leg.''
''It look like [Frye] was tangled in the horse for a wee period of time before she got cleared when the horse was trying to get up.''
Stewards called for the autopsy as the fractures were consistent with the horse falling to the ground, which indicated the problem - later discovered to be the artery rupture - happened prior to the fall.
McIntyre said the primary concern yesterday was to get Frye to the hospital. The stewards have embargoed the video footage and will go over it further at the first chance, he said.
Frye was transported to Ashburton Hospital before she was placed in an induced coma for the helicopter flight to Christchurch.
Her father Danny Frye, a former jockey, and her partner, fellow jockey Matthew Cropp, travelled to Christchurch to be by Frye's side, McIntyre said.
Frye rode 41 winners in her debut season, earning her the 2012-13 South Island apprentice jockey of the season award.
She has ridden 34 winners this season, including listed wins with Orovela in the Canterbury Belle Stakes in September, and Esprit D'Or in the Metropolitan Trophy in November.
