Chief steward Ray Murrihy says rugby league great Andrew Johns and retired jockey Allan Robinson "are parties of interest" in an investigation into the defeat of More Joyous at Randwick on Saturday.

More Joyous' owner John Singleton has accused bookmaker Tom Waterhouse of telling people the champion racemare More Joyous could not win the All Aged Stakes.

The glamour galloper is trained by the bookmaker's mother Gai Waterhouse with Singleton ending a 35-year association with the trainer after the race.

At a trackside inquiry on Saturday, Singleton refused to divulge the names of "trusted friends" who had told him Tom Waterhouse was saying there was a problem with More Joyous.

But Johns has released a statement on Tuesday dismissing claims Tom Waterhouse tipped him off about the condition of More Joyous.

Former jockey Robinson has reportedly said he rang Singleton about More Joyous after speaking to a friend who had spoken to Johns.

Robinson said Johns had been told by Tom Waterhouse "not all was right" with More Joyous, News Ltd reported on Tuesday.

"As we indicated we wanted to take this week to gather the evidence and as a part of that our intelligence and surveillance unit members will be interviewing a number of parties," Murrihy told racing network TVN.

"Obviously ... Andrew Johns and Allan Robinson would be a couple of parties of interest.

"We want to have a look at what information is available.

"We would have a look at those statements as to whether they're called (to the inquiry) and whether they're evidence is central to the two or three matters that these inquires will cover.

Murrihy said the public nature of the controversy had hindered the early stages of the Racing NSW investigation.

"The fact they have been publicly played out isn't terribly helpful but we'll have a look at how the evidence falls on Monday," he said.

Gai Waterhouse was at the Warrnambool race meeting in western Victoria on Tuesday where she spoke at a private lunch, but declined to comment on the affair.