Jockey Club stipendiary stewards have opened an inquiry into the reason for recent Class-Five winner Namjong Sky having swabbed positive to the drug omeprazole. Yesterday, the racing laboratory head Dr Terence Wan See-ming advised stewards that the urine sample taken from Namjong Sky after his win in the Yuen Wo Handicap last Wednesday was found to contain omeprazole and its metabolite, hydroxyomeprazole. Omeprazole is understood to be the active ingredient in a stomach ulcer treatment commonly used by a number of trainers at Sha Tin. It is a treatment approved by the Jockey Club veterinary department and, like most therapeutic drugs of its kind, it carries recommended withdrawal times before a treated horse can race. Yesterday, the stables of trainer David Hall were visited by stipendiary steward Philip Dingwall, veterinary officer Dr Kenneth Lam and members of the Jockey Club's security department, and Hall was advised of the analyst's finding. Hall has requested that the B portion of Namjong Sky's urine swab sample be forwarded to an outside laboratory for independent analysis. The club has agreed with the request, but Hall has not yet specified which international laboratory he would like to conduct the analysis. Until the B sample is analysed, the stewards cannot take their inquiries any further, so acting chief steward Kim Kelly has adjourned the inquiry to a date to be fixed. Under the Club's rigid drug-free rules, if the presence of a 'prohibited substance' is confirmed in the swab sample, stewards will have no alternative but to disqualify Namjong Sky as the winner of the race and award it to runner-up Sound Of Silence. The chestnut gelding had been winless in 19 starts until the end of last season, but has turned it all around this term, thanks to a total change in riding tactics. Now ridden cold in the early stages and allowed to finish his races off, Namjong Sky has been a transformed horse and the ease of his win in the bottom grade on National Day made him appear certain to cope with the rise in company once the handicapper pushed him into Class Four. The five-year-old first started at the stables of Me Tsui Yu-sak in early 2007.