Newcastle trainer Darren Smith has been placed on notice by Racing NSW stewards following a stable visit by the integrity unit on Thursday.

The integrity officials arrived only hours before Smith was to due start My Last Fling, The Gallows and Ladyinxs in support races at the Newcastle Cup meeting.

Smith and two of his stable staff were interviewed by stewards at Newcastle on Thursday after three containers of an amino acid called BCA Paste were found.

One was placed outside the stall of Ladyinxs who finished seventh in the Provincial Cup.

Deputy chief steward Greg Rudolph said stewards were not satisfied that any of the three runners had been treated and that was why they had been allowed to start.

However, Rudolph said the trio had been swabbed and the inquiry adjourned until the results were known.

"This is not the end of the matter," Rudolph told Smith.

"Your stable comes under our notice far too often.

"You are being put on notice that you will be coming under our scrutiny and can expect unannounced visits to your stable."