The Racing Integrity Unit has opened an inquiry into the death of a jockey who fell at a horse meeting in Gore.

LISTEN ABOVE: Jockey Association national president Dave Taylor spoke to Mike Hosking

Mother-of-three Rebecca Black's horse appeared to stumble and fall in race eight of yesterday's Tapanui Racing Club meeting.

The trailing horse had nowhere to go and also fell, and appeared to land on the 40-year-old jockey.

That horse had to be euthanised, but its rider escaped without major injury.

A second ambulance was called to assist the one already there, but Ms Black had died by the time it arrived.

Ms Black's former husband Kelvin Tyler confirmed two of her three children saw the accident unfold.

"They're obviously pretty shocked and devastated," he said. 

He had not seen a video of the accident but thought the horses might have got too close to each other.

"It sounded like it got a bit tight for room and they went down."

He said horses were Ms 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 Ms 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."

Police are preparing a report for the coroner and WorkSafe have been advised.

The race meet was called off after the fall.

Ms Black was based in Riverton, and rode on the South Island thoroughbred racing circuit.

During her career she had ridden in 1264 races, winning on 108 occasions. She rode her first winner in the 1993-94 season.