Classic-winning jockey George Baker was in intensive care in a Swiss hospital on Sunday afternoon after a fall at St Moritz.
Baker, who won the St Leger in September on Harbour Law, was riding Boomerang Bob for Jamie Osborne on the frozen lake track in Switzerland when the horse was brought down and was fatally injured in the first race of the day.
Three horses came down in the incident but the other two and both of their riders escaped injury.
Backer was taken to a trauma hospital in Chur and the rest of the meeting was abandoned with a hole in the course.
Baker's agent, Guy Jewell, said: "George is in intensive care at the hospital.
"The one bit of good news so far is that he has already had a CT scan and that has come back clear.
"Now all we can do is wait for the medication to wear off."
A statement issued on www.whiteturf.ch read: "After thorough investigation by the persons responsible for White Turf, a crack in the ice had occurred on the inner rails in the direction of the racetrack, some 150m from the finishing line.
"This meant that water had come up to undermine the racetrack."
Thomas C Walther, President of the Management Board of the St. Moritz Racing Association, told spectators: "As we could not estimate how conditions on the racecourse would develop, we unfortunately had to call off the race meeting.
"The safety of the horses and the riders are paramount. There is no danger for spectators anywhere on the lake."
