Apprentice Kristy French was taken to hospital following a nasty fall at Lingfield.
The 7lb claimer was unshipped from Marti's Boy, trained by Stan Moore, inside the final furlong when out of contention in the 32Red Casino Claiming Stakes.
Racing has been delayed until all the emergency services are back in place.
"The plan will be to get going as soon as possible and then catch up with the remaining races. If we resume shortly after 2.15pm we are hopeful of catching up with the rest of the races throughout the afternoon," clerk of the course Neil Mackenzie Ross told At The Races.
"First and foremost Kristy's health is the most important. That has to be first and foremost in everyone's mind."
