The fall happened during race 8 and the meeting has been called off.
A police spokesman said they were called to the meeting at 4.10pm and a jockey had died after falling from the horse.
He would not confirm the identity of the jockey, but the Otago Daily Times understands it was Rebecca Black.
Ms Black is 40 years old according to the NZRacing website.
She was riding Point Proven in race eight when her mount stumbled and fell, dislodging her from the saddle. The trailing horse Misscattlecreek ridden by Terry Mosley had nowhere to go and also fell and appeared to land on Black. Mosley escaped without major injury.
Black's former husband Kelvin Tyler confirmed two of her three children saw the accident unfold.
"They're obviously pretty shocked and devastated," he told the Herald.
He had not seen a video of the accident but thought the horses might have gotten too close to each other.
"It sounded like it got a bit tight for room and they went down."
He said horses were Black's number one passion. She had grown up with horses all her life. Tyler said she had close to 20 horses and ponies as Black ran a riding school as well as working as a jockey.
"She was a horse person.
"It's all she does and she's good at it."
Ms Black was a Southland-based jockey who rode on the South Island thoroughbred racing circuit. During her career she had ridden in 1264 races, winning on 108 occasions.
The race meet was called off after the fall, and police said they would compile a report for the coroner.
Worksafe were also in attendance.
