Queensland stewards have opened an inquiry into a fall which has left two Toowoomba track riders in intensive care with serious spinal injuries.

Ben Saunders and Wade Clasohm were riding trackwork early on Saturday morning when their mounts apparently collided sending both riders to the ground.

Trackwork was closed at Toowoomba for more than an hour while ambulance men attended to the pair.

They were initially taken to the Toowoomba General Hospital but then transferred to the Princess Alexandra Hospital in Brisbane on Sunday.

A spokeswoman for the Princess Alexandra Hospital said both remained in the intensive care unit and were ventilated and sedated and in a stable condition.

The spokeswoman said she could not comment further on their conditions but it is understood both will require extensive surgery.

Queensland Racing Integrity Commission chairman Ross Barnett said there would be a full inquiry into the incident after initial inquiries were made on Saturday and Monday.

"There were two horses involved. One was an unnamed a two-year-old which broke down and was euthanised. The second horse, a three-year-old escaped serious injury," Barnett said.

"Toowoomba stewards were on site shortly after the incident occurred, as they were there to inspect the track for the Toowoomba Weetwood race meeting later that day, and commenced investigations into the fall.

"My thoughts are with the injured track riders and their families at this time."

WorkCover Queensland will also investigate the incident.

In a bleak day for racing on Saturday, popular country NSW jockey Darren Jones died after a three-horse fall at Warialda in the state's north-west.

Apprentice Melanie Bolwell suffered bleeding on her brain in the incident and is being kept sedated in the Gold Coast hospital before doctors make a decision whether she needs surgery.

Leanne Henry also came down in the fall and suffered concussion and a broken collarbone.

She is expected to be out of action for six weeks.