2 | Background – Immigration detention in Australia Chart 2: Detention population total and by s 501 cancellation – January–December 202328 1200 1099 1061 1128 1117 1114 1110 1079 1056 1000 1005 987 878 800 621 646 689 702 716 697 696 675 643 872 628 600 538 531 400 200 0 Jan Feb Mar Apr May Jun Overall detention population numbers Aug Sep Oct Nov Dec Number of people detained under s 501 As of 31 December 2023, the detained population was made up of the following groups: 2.4 Administration of the detention network • Since 1 July 2015, the ABF has been responsible for administering detention operations and removals; while the Department remains responsible for the overall policy framework for detention, as well as matters relating to visa processing, and status resolution. External contractors play a central role in the management of immigration detention facilities. Serco Australian Pty Limited (Serco) is the contracted detention services provider, responsible for the dayto-day running of the facilities including security and provision of services and activities. International Health and Medical Services (IHMS) is the contracted health services provider, responsible for providing onsite physical and mental health services to people in detention. • • 14 Jul 531 people subject to visa cancellations under s 501 115 asylum seekers who arrived by boat 226 categorised as ‘other’ (including people whose visa was cancelled under other provisions, people who had overstayed their visa, unauthorised air arrivals, seaport arrivals and illegal fishers).29