A 14-year-old boy has been bailed by police pending further inquiries into the death of Carson Price, 13.
Carson, of Hengoed, Caerphilly, died after being found unconscious in Ystrad Mynach Park on Friday 12 April.
Gwent Police arrested the boy at Pontllanfraith, near Blackwood, on Thursday on suspicion of supplying class A controlled drugs.
The force said it had released the boy and it was seeking "charging advice" from the Crown Prosecution Service.
On Friday, hundreds of people gathered to release balloons in Carson's memory at the park where he was found.
In a statement released at the vigil, Carson's family said: "We have been truly overwhelmed by the support we have received locally, nationally and from around the world.
"Thinking of another family going through what we have is unbearable. We urge people to talk about the devastating consequences that drugs can have and how they destroy lives."
Police have said that drugs were involved in Carson's death.
A form of MDMA, known as Donkey Kong pills, is also a line of inquiry.
The force said it received a separate report that a man became "seriously ill, requiring hospital treatment" from Donkey Kong pills over the past week.