Three people have been taken into custody for questioning about the murder of Daniel McAnaspie.
The three - a 17-year-old girl, a man, 23, and a woman in her 40s - are being detained at Finglas and Blanchardstown Garda Stations on suspicion of allegedly withholding information.
The body of 17-year-old Daniel McAnaspie, who had been in the care of the State, was found in Co Meath last month.
Detectives believe he was stabbed with a garden shears in the Tolka River Valley near Whitestown where he went missing in February.
His body was taken from there and dumped in a ditch in Gilliamstown, Rathfeigh, in Co Meath.
A total of seven people have so far been arrested as part of the investigation.
