10News learned a horse was hurt during the 7th race on the turf course, and a source said the horse's injury to its front left leg was considered "serious."
The injury was the first since the turf course was reopened Wednesday. Some changes were made to the course after four horses had to be euthanized following injuries suffered on the turf.
Track officials said the closure would run through Sunday, with next Wednesday possibly being the next time a race is held on the turf course.
Officials released this statement regarding Thursday's closure:
Del Mar Thoroughbred Club feels deep sorrow and great concern following a further injury on our turf course during racing on Thursday afternoon.
We continue to be of the belief that Del Mar's turf course is safe for our horses and riders. Our crews have performed extensive maintenance measures to enhance that safety and those measures - and the course itself - met with the approval of safety officials from the California Horse Racing Board this past Tuesday.
Nonetheless, given this additional injury on our turf course, we now will discontinue racing on it for the remained of this week. We will continue efforts to improve the course during this down time and hope to resume racing on it in the near future.
Further, we also will continue our communication with all our partners in the racing community - the California Horse Racing Board, the Thoroughbred Owners of California, the California Thoroughbred Trainers and the Jockey Guild - in attempts to understand and solve this serious problem.