Police are investigating whether the use of illegal drugs caused the death of a 13-year-old boy.
Carson Price, of Hengoed, Caerphilly, was found unconscious in Ystrad Mynach Park at about 19:20 BST on Friday.
The teenager was taken to University Hospital of Wales in Cardiff where he was pronounced dead.
His family paid tribute, saying he was “the best big brother” who would be missed by many.
Gwent Police is treating the boy’s death as unexplained and specialists are working to determine the exact cause of death.
Det Ch Insp Sam Payne said: “Although we await official medical confirmation of the cause of death, one of our main lines of enquiry focuses on illegal substances being a contributing factor.
“Specialist officers continue to support Carson’s family through this difficult time.”
In a statement, his family said: “Carson was bright and caring, kind and loving, he was a cheeky little boy.
“He was the best big brother and was loved and will be missed by so many.”
A local councillor expressed his sympathies with Carson’s family, adding that he hoped his death would deter other youngsters from taking drugs.
“If it is a drug-related passing, I just hope that young people realise that you shouldn’t really deal with drugs,” Councillor Martyn James said.
“You have got to leave it alone because unfortunately – we know all too well now – we have lost a young man and his life has gone.”
Meanwhile, flowers have been laid at the park close to the spot where Carson was discovered on Friday evening.
Chris Parry, head teacher at Lewis School Pengam, said everyone at the school was “devastated at the terrible news”.
Mr Parry said the school would be providing support for all pupils and staff affected.