Police have issued a fresh warning over the dangers of drugs after a 15-year-old girl died in Cornwall.
The girl, named locally as Shakira Pellow, collapsed in Camborne on Friday and died in hospital on Saturday.
It is not known what substance she took but police said it had been seized and was being tested.
A family member said Miss Pellow could "light up a room" and had been upbeat "talking about her future and going to college".
The woman, who did not want to be named, said: "She could walk into the room, light it up - she was just a good kid.
"I wouldn't even want to wish it on my worst enemy. It's absolutely devastating for anyone that could have seen Shakira the way she was."
Det Supt Roy Linden, from Devon and Cornwall Police, described it as a "truly tragic incident".
He said: "We want to warn children and young people of the dangers surrounding taking drugs.
"We ask parents and carers to speak to their children about the risks associated with drugs."
He added: "It is believed that all four teenagers were initially hanging around a scrapyard near Tesco, before heading back to the home of one of the teenagers.
"All four have then gone on to Pengegon Park. A short time later the 15-year-old girl collapsed and an ambulance was called."
A 15-year-old boy and two teenage girls were taken to hospital after taking the same substance and are all expected to be discharged.
Facebook tributes have been paid to the dead girl, who was originally believed to be aged 14. She has not yet been officially identified by police.
Sid Willett, from the Cornwall Drug and Alcohol Action Team, said the substance involved could cause "fitting, overheating and severe irritation".
He told the BBC: "You can bet your bottom dollar this drug could be in every corner of the UK.
"It is possible these tablets could have come from abroad or on the dark web".
Among tributes paid to Miss Pellow on Facebook, Kathryn Yeoman said: "I am shocked!... Such a lovely young lady gone far too soon."
Jessie James said: "She had an amazing soul and was so beautiful... She will be missed by so many people."
Victoria Soares described it as the "saddest heartbreaking news ever".
Two 17-year-old boys, one from Camborne and the other from Redruth, were arrested on suspicion of being concerned in the supply of a controlled drug. They were later released on bail, officers said.