More than 30 homes in 12 counties have been searched as part of an investigation into the possession and distribution of child abuse images.
The raids, under Operation Ketch, were carried out over the past three days and computers, phones and other equipment have also been seized.
Gardaí have said the evidence gathering phase of the operation was now complete and arrests and charges are expected.
They have also said their first priority is to try to identify if any of the children in the images remain in danger.
Gardaí said the investigation by the Online Child Exploitation Unit at the Garda's Protective Services Bureau has been under way since last year.
Operation Ketch was set up to target people suspected of possessing and distributing child exploitation images.
As well as their own inquiries, gardaí received information from law enforcement authorities in the US and Canada, and secured warrants in court to search designated addresses in Ireland.
Searches began last Saturday and continued today in homes in counties Dublin, Wicklow, Kildare, Limerick, Kerry and Waterford.
Computers, phones, iPads, laptops, documentation and other material has been seized.
Det Supt Declan Daly outlines details of Operation Ketch pic.twitter.com/zO0BBVqWKm— Will Goodbody (@willgoodbody) February 5, 2018
Detective Superintendent Declan Daly of the Garda National Protective Services Bureau said Operation Ketch aimed to target suspects in possession of and distributing child exploitation material.
He added that an additional aim was to provide a level of assurance to the public of the critical importance put on child protection by An Garda Síochána.
It also served as a stark warning to those who possess, distribute or produce such imagery that their homes would be searched, their sexual interest in children would be exposed, and ultimately that they could be prosecuted and convicted.
The operation was led by the Online Child Exploitation Unit with the assistance from the Garda Cyber Crime Bureau and divisions nationwide.
He said 31 homes were targeted and searched under warrant but right now there was no known connection between any of the suspects.
There have been no arrests so far but they will follow when the material has been examined, he said.
Det Supt Daly said it was not clear how many children were involved or if any were in Ireland, but in all cases where there was a child protection risk in the home that Tusla was informed.
He said the task of examining the material and the arrests of the suspects begins now.
The operation was also timed to coincide with Safer Internet Day, which takes place tomorrow, and Det Supt Daly reminded parents and children to use the internet safely.
He underlined the importance of having good communication so that children can inform parents if they receive suspicious approaches on social media.
If a request for images is received, children should not send them and tell a parent or adult, and then preserve the communication and block the communication before informing gardaí.
Assistant Commissioner John O'Driscoll said tens of thousands of images were on the devices that were seized.
He said the investigators ambition is to ensure arrests they make are timed so as to maximise the possibility of success from any prosecutions that might ensue.
As a result, he said, it would take some time to go through it all.
He added that arrests could start this evening or over the next few days.
Det Chief Supt Daly said in general the profile of those typically involved in these activities was male, professional, aged between 25 and 50, with medium to exceptional IT skills.
He said the general perception of a perpetrator being someone operating out of a basement or dark room was not actually correct.