Gardaí have confirmed that no DNA evidence has been found to link the disappearance of Philip Cairns to convicted paedophile Eamon Cooke.
The 13-year-old schoolboy went missing from south Dublin in October 1986.
His schoolbag was found dumped in an alley close to his Rathfarnham home six days later.
A garda spokesperson said forensic samples from the bag have not established a connection with “any named individual”.
However, it is understood that Cooke remains a suspect in the investigation.
The former radio DJ died in June while serving a 10-year sentence for sexually assaulting two girls.
Detectives opened new lines of inquiry in the case after a member of the public came forward with new information in May.
Personal items such as documents, diaries and tapes are still due to be examined as part of the probe, gardaí said.
Anyone with information has been asked contact the garda confidential line on 1800 666111 or any garda station.