A horse trained by Chris Waller has returned a positive test to the drug ice.

Fairfax Media reports the trainer of Australia’s best horse, Winx, could have to face a stewards’ inquiry into the positive sample to methamphetamine from one of his horses if it is confirmed by a second sample.

The horse in question has not won a race.

Fairfax Media understands an investigation has been opened, with stable staff from the Waller yard to be drug tested.

‘It is an issue we want to get on the front foot with and we have tested our staff to try and find how this happened,’ Waller told Fairfax Media.

It comes on the same day Winx, the two-time defending Cox Plate champion, was rated the best turf horse on the planet.