Philip Cairns from Rathfarnham in Dublin went missing in October 1986 during his lunch break – his backpack was later recovered close to his home.
It's understood a woman came forward to Gardaí following an appeal for information claiming to know who killed the 13-year-old.
Garda suspicions are reportedly focused on the former pirate radio DJ Eamon Cooke.
He was sentenced to 10 years in prision in 2007 after being convicted of multiple indecent assaults on two young girls.
Mr Cooke, who was 79, died in a Dublin hospice last week.
