Gardaí believe people who were children when Philip Cairns disappeared in October 1986 may have information about his schoolbag.
The Dublin schoolboy has been missing for almost 30 years, but new information has been given to gardaí in recent months.
One of the many lines of inquiry is that convicted paedophile Eamon Cooke, who died last week, was involved in the death of the 13-year-old.
Philip Cairns (pictured) was on his way back to school in Rathfarnham when he disappeared without a trace.
His schoolbag turned up days later in a nearby laneway - and gardaí now believe that bag, and whoever placed it there, could move the case along. It is thought two to three schoolgirls may have been coerced into leaving the bag in the laneway.
DNA samples found on the schoolbag have been sent for analysis.
Superintendent Peter Duff of Tallaght garda station said: "We are anxious to hear from anyone who may have knowledge of how the schoolbag came to be in the laneway, who may have seen it being put there or may have observed it there at any time."
A woman came forward after the 25-year appeal for information. Gardaí say her statement has opened up 160 lines of inquiry; among them, that convicted paedophile Eamon Cooke was involved.
Superintendent Duff (pictured below) said Cooke's death earlier this month may enable witnesses to come forward now.
"Maybe the publicity has jarred someone's memory," he said.
"We will treat anyone who comes forward sensitively and discreetly because I am very aware that some people may have suffered trauma in the past and may now feel more secure in coming forward," he said.
Superintendant Duff added: "For the sake of Mrs Cairns and her family who have been suffering for 30 years it is important that we bring this investigation to a conclusion.
"I am again appealing to anyone who has information in relation to Philip’s school bag and have yet to come forward, to contact Rathfarnham Garda station on 01 666 6500, the Garda Confidential Line on 1800 666 111 or any Garda station."