Trainer Greg McFarlane is facing serious penalties including jail after being caught trying to stomach tube a racehorse two hours before it was due to race at Rosehill on Saturday.

After initially denying the horse was Ferocimo, McFarlane later admitted to stewards it was in fact the gelding which was scheduled to race.

In May, northern NSW trainer Cody Morgan became the first licensed person charged after changes to the NSW Crimes Act which state those found guilty of fraudulent conduct or to have inside information that potentially could affect betting outcomes on an event including a horse race, face penalties that could result in up to 10 years' imprisonment.

The NSW Rules of Racing now carry a minimum 12 month-disqualification for anyone found guilty of attempting to or being present when a horse is treated with any substance within 24 hours of a scheduled race.

Racing NSW detective Albert Gardiner went to McFarlane's Rosehill stable at 1.10pm where he found stablehand Carmen Hepburn and the trainer with the horse which had a tube inserted in its nostril.

Gardiner and stewards took possession of a nasal tube, funnel, bucket and plastic zip lock bags containing a white powder.

Blood and urine samples from Ferocimo and other horses in the stable were also taken, a process that was repeated.

McFarlane initially told officials the horse was Belegic, who was not racing on Saturday, but later admitted it was Ferocimo who was withdrawn from the sixth race.

Although the tube had been inserted, McFarlane said the horse had not received any treatment.

He said Ferocimo had not received the treatment as he had been interrupted and admitted he had tried to pass him off as Belegic.

"It was a knee-jerk reaction," McFarlane said.

"There's not much I can say."

Stewards said McFarlane could continue training his horses while investigations were ongoing but he would not be allowed to race them with his acceptors at Wellington and Kembla Grange on Tuesday to be withdrawn.

McFarlane, a former top cyclist who just missed out on qualifying for the 2000 Sydney Olympics, said he was not a punter and did not operate a betting account.