None of the products Hong Liyuan and Hong Haihui have been feeding their 11-month-old son have been found to be contaminated with melamine, but the Dongguan couple were worried enough to take him for a check-up in Hong Kong yesterday. They were among the mainland parents taking their Hong Kong-born children to public clinics for free kidney check-ups during the National Day 'golden week'. 'We are not confident about mainland clinics ... we think doctors in Hong Kong are more detail-minded and trustworthy, so we decided to take him here for health checks,' Mrs Hong said at a Tuen Mun clinic. Another anxious parent was teacher Johnson Chi from Shenzhen, whose two-year-old son started to drink Mengniu and Yili milk six months ago. 'He has no symptoms at all, but I am still quite worried. We don't want him to have check-ups on the mainland. The clinics there are packed with patients. We fear doctors will see patients perfunctorily.' Speaking on a radio programme, Hospital Authority quality and safety director Leung Pak-yin said all five children who had been found to have kidney stones in Hong Kong had returned home. He said four of them had tiny kidney stones and had been told to drink more water to help discharge the stones from their bodies. Only a nine-year-old boy with bigger kidney stones had undergone an operation, Dr Leung said. By 5pm yesterday, the 18 designated clinics provided initial assessments to 2,100 patients, while nine special assessment centres had attended to 563 patients. In the 24 hours to 1pm, the Centre for Health Protection hotline received 552 inquiries, bringing to 8,423 the number of calls received by the hotline since it was set up on September 21. The Consumer Council's latest check found the price of milk powder had remained unchanged compared with about two weeks ago. It said it had been assured by big suppliers of infant milk powders that they would not change their wholesale price and would maintain a stable supply.