Trainer Francis Lui Kin-wai must face stewards after beaten favourite Supreme Winner returned a positive urine sample after the Sha Tin meeting on April 3. The head of the racing laboratory, Dr Terence Wan See-ming, advised the stipes yesterday that the horse's post-race urine sample contained omeprazole and its metabolite hydroxyomeprazole - two components of an ulcer treatment used for horses. An independent laboratory will now analyse the B sample and stewards have adjourned the inquiry to a date to be fixed.