Five babies in the same ward at Princess Margaret Hospital have contracted viral gastroenteritis.
The two boys and three girls in D1 ward, aged between 61 days and six months, have suffered diarrhoea since Saturday and all tested positive for rotavirus yesterday.
All five have been put in isolation and were in stable condition last night.
The Centre for Health Protection and Department of Health yesterday activated a green alert at the hospital, the lowest alarm for infectious diseases, and restricted visiting.
Visitors had to register and put on protective gear to visit the ward. The hospital also refused all new admissions to the ward, diverting some patients to Yan Chai Hospital.
Private paediatrician Leung Ying-kit said it appeared there had been a breakdown in the hospital's infection-control measures.