South Australian jockey Caitlin Forrest has died in hospital overnight from injuries suffered in a fall at Murray Bridge yesterday.

The 19-year-old had been leading the race when her horse broke down at the halfway stage, bringing down three other horses.

She was flown to the Royal Adelaide Hospital but died overnight.

Fellow jockey Libby Hopwood was taken to the local hospital before being transferred to the Flinders Medical Centre in Adelaide.

Another jockey, Justin Potter, received minor injuries but was treated and cleared at the scene.

Partner Scott Westover paid tribute to her on Facebook, saying he had lost the love of his life.

Forrest's mount, Colla Voce, had to be put down.

Race caller Terry McAuliffe said it was one of his most difficult days at the race track.

"It's the worst possible scenario when we have a race fall horse at the front of the field," Mr McAuliffe said.

Thoroughbred Racing SA said they will conduct a review of the incident.

Yesterday's incident followed the death of Queensland jockey Carly-Mae Pye after a fall during barrier trials at Rockhampton on Monday.