At least 100 complaints of sexual abuse were made to gardaí against the Christian Brother who was jailed on Tuesday for sexual abuse of boys at Letterfrack Industrial School.
Maurice Tobin pleaded guilty to the abuse of 25 boys at the Co Galway school over a 15-year period up to 1974. He received a 12-year prison sentence, with the last four years of it suspended.
During the hearing in Galway at which he was sentenced, the court heard how he systematically molested, abused and buggered boys aged from 11 to 14 who were sent to work in the kitchens.
A number of the victims told of the devastating impact of the abuse on their lives.
It has now emerged that during the Garda investigation, investigating officers took complaints from at least 100 former residents who said they were sexually abused by Tobin.
It is one of the largest number of complaints ever made against a single abuser in the State, and followed one of the largest investigations of its kind.
Tobin is still a member of the Christian Brothers. He had been working and living in north Dublin at a home for elderly brothers. The 71-year-old's duties included driving the home's minibus.
The investigation into Letterfrack is continuing. The four-year inquiry has involved six gardaí, with two working full-time on the case.
Detectives took hundreds of witness statements from former residents around the country alleging abuse at Letterfrack.
In a statement on Tuesday, the Christian Brothers apologised to Tobin's victims.
The order said that Tobin was the first member to have been convicted in relation to abuse at an industrial school. "The Christian Brothers deeply regret the hurt and pain caused to those who were abused by Brother Maurice Tobin," the statement said.
However, a former member of the order was convicted last year and given a three-year suspended sentence for abusing boys at Letterfrack between 1968 and 1970.
John McKenna (59) of Wood Dale Green, Ballycullen, Dublin, pleaded guilty to the charges.
The Letterfrack investigation also involved the exhumation of the body of a boy, Willie Delaney, in April 2001, who had died soon after he was released home from Letterfrack in July 1970. He had been sent to Letterfrack in 1967 for stealing a bicycle.
The gardaí had received allegations that the boy had received a beating with a flagpole by a brother before he had been sent home. The post-mortem revealed the boy had died from an untreated infection.
Investigating gardaí were told that the infection could have been easily treated with antibiotics, which were widely available at the time.
The post-mortem also found evidence that the boy had received a blow to the head.