Police are investigating more than 250 complaints of the abuse of children living in residential care in Northern Ireland.
Most of the 251 cases being examined by Operation Charwell relate to incidents at least 20 years ago, but some date back 40 years.
Assistant Chief Constable George Hamilton, the officer in charge, has deployed special resources from public protection units and the rape crime unit.
A statement said: "Investigations are being conducted on a case-by-case basis, focusing on the interests of victims, with the aim of providing justice where possible, and mindful of the absolute need to protect individuals who may be currently at risk."
Mr Justice Anthony Hart, a retired High Court judge, will also head an official inquiry into the abuse of children in residential care in the autumn.
It will assess whether there were systemic failings by the state or institutions in their duties towards children under 18 in residential care.