A recent winner at Sha Tin had a banned substance in its system but no action will be taken as Jockey Club officials believe no rule has been broken.
The South China Morning Post believes the horse involved to be the John Moore-trained Ming Hoi Treasure and the banned substance to be cocaine.
The matter is now in the hands of the security department and the trainer has been informed so he can take whatever measures he deems fit to improve stable routine.
Chief steward Kim Kelly yesterday acknowledged the presence of 'a substance' uncovered in post-race tests by the club's analyst, but would neither name the substance or horse involved as it did not constitute a positive drug test. 'A substance has been detected, in an extremely low level, from a horse which raced recently,' Kelly said.
'The sample detected was of such a low level that there were no metabolites found and the analyst has formed the view that the presence of the substance could have had no influence on performance.
'Furthermore, the analyst says the evidence is overwhelming that the level detected would very likely be due to inadvertent exposure of the horse to the substance close to the race.'
Kelly said he had spoken to the trainer of the horse as a courtesy.