The racing community is reeling after jockey Simone Montgomerie died following a race fall during the Darwin Cup meeting.

Champion jockey Nash Rawiller said he had never left a racecourse feeling so sad and numb, while trainer Lee Freedman said the whole racing industry feels the pain.

From a noted racing family, Montgomerie, 26, was thrown from her mount Riahgrand when she was coming down the home straight in the sixth race of the day at Darwin Racecourse on Monday.

The mother of two tumbled off her horse and was trampled by the rest of the pack.

Two doctors treated her at the scene, but Ms Montgomerie passed away shortly after arriving at Royal Darwin Hospital.

"I've never left a racecourse feeling so sad and numb!" tweeted Rawiller, who was in Darwin for the Cup.

"Great jockey and beautiful young lady. Thinking of her family and close friends."

Hall of fame trainer Freedman said words couldn't express his distress at the news of her death.

"They face such danger. Everyone in racing feels this pain," he tweeted.

Jockey Kerrin McEvoy said he would remember the pony club days he shared with Montgomerie forever.

"It's a cruel game at times. Rest in peace Simone. Thoughts go out to the big Mont family," he wrote.

Montgomerie, whose father Peter Montgomerie trained the 2005 Melbourne Cup runner-up On A Jeune, was indentured to South Australian trainer David Jolly in the early days of her apprenticeship.

"The news has really hit home hard. The racing fraternity will stay strong and support!" Jolly tweeted.

A full investigation into the circumstances of the accident has already been initiated by stewards, said Darwin Turf Club chairman Brett Dixon.

"As far as the Darwin Turf Club is concerned, she was our family, and we're all devastated by this accident," he told a press conference.

Mr Dixon said Montgomerie suffered traumatic injuries.

The rest of the carnival, including the Darwin Cup itself, was cancelled after officials spoke with distraught jockeys.

NT Chief Minister Adam Giles said it was a sad day for the Australian racing industry.

"Simone was a champion jockey at the top of her game and a pioneer of women in racing who will be sorely missed," he said in a statement.

National Jockeys' Association general manager Des O'Keeffe says the organisation will support Ms Montgomerie's family.

"We also have support for any jockeys who need it. We have counselling services they can ring," he said.

"It is unbelievable that this has happened just two days after National Jockeys Celebration day around the country. I have had many jockeys ring me and they are absolutely shattered."

National Jockeys Celebration day was held on Saturday by the National Jockeys Trust which provides support for families of killed and injured jockeys.

Recently, Gold Coast-based New Zealander Ashlee Mundy was home for the summer circuit when she died on December 30 after a fall at Kurow, while Corey Gilbey was killed in a fall at Julia Creek in Queensland on November 12, 2011.