Caitlyn Fischer, 19, from Bairnsdale, Victoria was fatally injured after falling from her horse in the cross-country competition at the major equestrian event.

Organisers said Ms Fischer was riding the horse Ralphie in the one star competition when the accident occurred at fence two at about 10.40am.

She was provided urgent medical attention by the on-course paramedic and doctor but could not be revived.

Her horse, Ralphie, is in a stable condition and remains under the observation of veterinarians.

It is understood that Ms Fischer worked for elite equestrian Christine Bates.

The trials have been cancelled and police investigations are underway.

In a statement, Equestrian Australia chairwoman Judy Fasher said, "On behalf of the whole sport I would like to extend our deepest sympathy to Caitlyn's parents Alissa Carr and Mark Fischer and her family. The thoughts and prayers of horse people all over the country are with Caitlyn's family and friends at this sad time."

Bairnsdale Pony Club district commissioner Janine Bromwich said Ms Fischer was a "gorgeous, beautiful girl" and came from a "great Pony Club family".

She said the competitor had been involved with the club for about 10 years, before she finished year 12 at Gippsland Grammar School and moved closer to Melbourne.

"She was a really intelligent girl," Ms Bromwich said.

"She was part of our state games team and she actually left Pony Club to pursue horse trials.

"Her parents were taking her down to Melbourne so she could compete.

"She was very, very committed in everything she did ... just a bright, bubbly kid."

The accident comes only weeks after schoolgirl and showjumper Olivia Inglis, 17, died while competing at the Scone Horse Trials in the Hunter Valley.

In a Facebook post at the time, Ms Fischer paid her respects to Ms Inglis, commenting "‪#‎rideforolivia‬" alongside an equestrian image. 

More to come