The Centre for Health Protection is investigating an upper respiratory tract infection outbreak at a kindergarten in Yau Tsim Mong District, involving 23 children aged three to five.
The 21 boys and two girls have fallen ill since September 7. They are in stable condition.
The centre's officers inspected the centre and gave preventive advice to its staff.
The centre appealed to the public to maintain strict personal and environmental hygiene to prevent infection.
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