The three teenagers who were treated for poisoning on Halloween are still recovering in hospital.
Three victims are still in St James', St Vincents and the Mater hospital.
All three consumed a clear liquid on Halloween and became very sick.
It is understood that the substance they consumed was acid-based.
Gardai are now following a definite line of inquiry.
Investigators however believe that the incident was not malicious but they do want to know where the liquid came from and who passed the substance to the youths.
Bridewell gardai have been carrying out door-to-door interviews during the week.