Police in Northern Ireland are investigating more than 250 complaints of clerical and institutional abuse.
Some of the allegations go back 40 years, according to the Police Service of Northern Ireland.
With retired High Court judge Mr Justice Anthony Hart set to head up an official inquiry into the abuse of children living in residential care, police said the vast majority of the 251 complaints under their investigation - Operation Charwell - relate to incidents at least 20 years ago. But the overall time range was five years to 40 years.
Assistant Chief Constable George Hamilton, the officer in charge, has deployed special resources from public protection units and the rape crime unit, according to the police.
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."
Organisations who ran institutions as far back as 1945 will face pressure to explain the treatment of young people once the Hart Inquiry gets under way in the autumn.
The Stormont Executive is looking to have a full report on the findings and recommendations ready in three years' time. The inquiry will assess whether there were systemic failings by the state or institutions in their duties towards children under 18 for whom they provided residential care between 1945 and 1995.
Meanwhile, the police appeared to rule out any follow-up investigation in their jurisdiction linked to a BBC TV documentary in which it was claimed Cardinal Sean Brady failed to act after being alerted to abuse allegations when he was a young priest.
The programme revealed that in 1975 a teenage boy who had been sexually abused by the paedophile priest Father Brendan Smyth gave the then Father Brady the names and addresses of other children who had been abused.
Friday's statement said: "The PSNI have examined the content of the recent BBC programme relating to historical child abuse and the Catholic Church and have conducted a number of inquiries. Whilst we do not comment on the specific details of any investigation, we can confirm that none of the allegations within this programme occurred in Northern Ireland."