The pressure facing Silent Witness' trainer Tony Cruz in the build-up to tomorrow's international trial meeting at Sha Tin took on a new dimension yesterday when stewards informed him one of his horses had returned a positive swab. Dr David Leung Kwan-kon, acting head of the Hong Kong Jockey Club laboratory, advised stewards the post-race urine sample provided by Cruz's Nasa Pearl had been found to contain the drug hydroxyomeprazole. This is the second known case of hydroxyomeprazole in Hong Kong and comes just five days after the initial case, when the Geoff Lane-trained Favourite Express tested positive to the drug, understood to be an active ingredient in a number of prescribed treatments for equine stomach ulcers. Nasa Pearl had urine and blood samples taken after his second to Perfetto in the final race at Sha Tin last Wednesday, although the blood samples have been declared negative. Stipendiary steward Kim Kelly, senior veterinarian Brian Stewart, Leung and a club security officer visited Cruz's Sha Tin stables yesterday morning. The B sample from Nasa Pearl will now be independently analysed.