Mundy (26) was flown to Dunedin Hospital after falling off Elleaye in race 7. Apprentice Toni Direen (Lemon Honey) was also dislodged in the accident at the 600m mark.
Co-chief stipendiary steward Nigel McIntyre said the John Sargent-trained Elleaye clipped a heel of a horse in front as the field came around the final bend, sending Mundy to the ground, causing injuries to her head.
''She's been airlifted to Dunedin Hospital in a critical condition,'' McIntyre said.
''We have opened an investigation into it and the police are here to interview the riders as as well, and that's just a precaution if there are any flow-on effects from it.''
Constable Craig Bennett, of Kurow, said the interviews were to determine the position of the riders during the accident, because of the severity of the injury.
Mundy recently returned to New Zealand to ride during the holiday period, having based herself on the Gold Coast in Queensland for much of 2012. She had spent Christmas Day with her parents in Westport before riding Fintorro to a win at Timaru on Friday.
She has ridden 232 winners in New Zealand, with her first win in August, 2004 on the Michael Pitman-trained Starkay. She has won four listed races, including the 2009 Dunedin Gold Cup on Never Plead Guilty.
Direen was stood down for the rest of the day, but suffered only minor cuts and bruises in the fall. She will be able to ride at Waikouaiti tomorrow.
