Nicholas Tse spent his first night in Pik Uk Correctional Institution under observation in the centre's hospital after doctors were told he was suffering from asthma.
He was admitted to the sick bay after he was body-searched and given a regulation prison haircut, a source said.
It is not known how long Tse will remain in the sick bay.
If he is found to have recovered sufficiently he will either be transferred to one of the 211 single-person cells or one of the 170 dormitories for between 12 to 20 inmates, the source said.
Apart from the normal daily exercises given to inmates, they also were allowed an hour's recreation each day, the source said.
Officers at Pik Uk yesterday declined to disclose any information on Tse, saying they would not comment on individual cases.