Approximately 25 race horses were killed when a wildfire engulfed about eight barns at a training centre in north-east San Diego County, the California Horse Racing Board said.

Horses that were in surrounding pastures remain unaccounted for.

Nearly 500 horses were stabled at the San Luis Rey training centre in Bonsall when the fire erupted amid strong Santa Ana winds on Thursday, a board statement said.

Training centre workers risked their lives to free horses from stalls and herd them into safer areas, the Horse Racing Board said.

When it was safe for vans to enter, surviving horses were transported to the Del Mar race track.

Los Alamitos Race Course cancelled its Friday racing programme out of sympathy for the owners, trainers and caretakers of the horses that were involved.