Undercover police officers are to patrol outside jails as an investigation into attacks on correctional institutions continues.
A special joint police-Correctional Services Department intelligence team began work yesterday.
CSD investigators have moved into Organised Crime and Triad Bureau headquarters in Causeway Bay.
'It will speed up our investigations and make them more thorough,' a police source said.
The latest incident in the series of attacks, in which an officer's car was set ablaze on Saturday outside Stanley Prison, coincided with a gathering of more than 1,000 CSD staff at their annual dinner in Tsim Sha Tsui.
It is believed that CSD units checked the Ocean Terminal restaurant where the dinner took place three hours before the start.
Asked about the possibility of former officers being involved in the attacks, a senior police source said: 'I don't want to suspect any ex-CSD staff, although it is possible.' Saturday's attack took place outside residential quarters in Tung Tau Wan Lane. Police said the perpetrators appeared well-briefed on the site, which lies up a steep slope and through thick vegetation.