Deputy Director of Health Dr PY Leung said a team of seven World Health Organisation experts will arrive from Canada and Australia this week to study the possible environmental transmission of atypical pneumonia.

They will stay for three weeks and target several buildings, including Amoy Gardens, for focused study, said visiting WHO's Senior Adviser Dr William Cocksedge.

Dr Cocksedge said the move is to supplement and follow up on studies and investigations already being conducted in Hong Kong. He said Hong Kong has done an excellent job.

On the possibility of withdrawing the WHO travel warning, Dr Leung said that will be determined by several factors: stability of virus cases; and, effectiveness of preventive/detective/monitoring measures against the virus spread.