Victorian trainer Glenn Thornton is at the centre of Racing NSW stewards' inquiry after a syringe was found in a stable occupied by Cool Attraction before she raced at Rosehill.

The trainer was questioned at length before the first race and the mare was allowed to run.

She finished fifth in the race won by Reply Churlish.

Pre-race and post-race samples were taken from Cool Attraction and also from the unused oral syringe and residue in a bucket taken from Thornton's car.

Stewards took evidence from Thornton and his wife Wendy before adjourning the inquiry to wait on the results of the tests.

The substance is promoted as a pre-race treatment.

Horses are not allowed to be treated on race day unless approval is given and the offence carries a mandatory six-month disqualification for the trainer.