Nati also confirmed that the two stewards, Paul O'Toole and Matthew Bentley, who are believed to have leaked information regarding which horses would be drug-tested, have so far co-operated with the investigation that is deepening every day.
"Obviously, we spoke to them. On top of what we already knew they provided additional information," he said.
Harness racing's image has been hammered by the scandal and Nati confirmed that class action would be taken against those found to be involved in the rort.
"It's an opportunity for HRNSW to draw a line in the sand and say that if you are found to have acted dishonestly we will put all our resources into making you accountable and if you cheapen our brand we want compensation. And that's what civil lawsuits are about," he said.
Asked how long he believed the fraudulent activities had been taking place, Nati replied: "It's probably not something I want to speculate on at the moment. I think in general terms, though, it is fair to say that it has escalated in recent months.
"And just for clarity and so people get a proper perspective, it was happening on a very small number of races. Of course once is one too many."
HRNSW has already begun taking action and opened an inquiry into why Darryl Thomas presented two horses, Points North and Zoro, to the races with elevated TC02 readings.
-AAP