Apprentice jockey Caitlin Forrest has died after a fall at Murray Bridge racecourse near Adelaide.

The 19-year-old suffered horrific injuries when her mount Colla Voce fell, bringing down three other horses, and she was flung to the ground ahead of the trailing pack on Wednesday.

She was reportedly semi-conscious and responsive when airlifted to the Royal Adelaide Hospital but later died from her injuries.

Also injured in the crash was Libby Hopwood, who was taken to Murray Bridge Hospital for observation.

Forrest's boyfriend, fellow jockey Scott Westover, said on Facebook: "Today has been the worst day of my life.

"I know there will be an angel up there watching me everyday and riding with me. Love you and I'll never forget you."

The news came in the same week another Australian jockey, Queensland-based Carly-Mae Pye, lost her life in a barrier trial at Callaghan Park.