A pool at a third swimming complex was shut yesterday after worms were found in the water. The closure of the children's pool at the Kwun Tong complex followed the complete shutdown of the popular Kowloon Park swimming complex on Monday, together with a children's pool at Tai Wan Shan near Hunghom. The closures came as leisure and health officials remained puzzled about the source of the small, red worms, which were first found at Kowloon Park on August 4. All the affected pools have been closed indefinitely, although officials said the other pools at the Tai Wan Shan and Kwun Tong sites could remain open. The Leisure and Cultural Services Department will clean the sand trap and filtration system at the Kowloon Park complex in an effort to find the source of the worms. Assistant Director of Leisure Services Paul Cheung Kwok-kee said this would take about 10 days and the pools should reopen early next month. Worms collected at Kwun Tong and Tai Wan Shan have been sent to the Food and Environmental Hygiene Department for tests. The Tai Wan Shan pool was drained on Monday. Cleaning efforts were stepped up at the Kwun Tong pool yesterday but the department had not decided last night whether it needed to be drained. Mr Cheung said investigations at the two sites would take a day or two. The worms found at Kowloon Park have been identified as bloodworms, the larvae of a species of mosquito that do not bite and do not constitute a health threat to the public, according to the department. The worms can be bought at pet shops as goldfish food. They continued to be found at Kowloon Park as recently as last Friday, despite clean-up efforts by the department. All the indoor pools were closed on Saturday and the remaining pools were shut on Monday. Mr Cheung said the decision not to close all the Kowloon Park pools on Saturday was out of consideration of the impact it would have on swimmers. But he said it was difficult to conduct a thorough investigation without closing the pools.