Three boys have been arrested in connection with the death of a 16-year-old girl who is thought to have taken an illegal drug.
Ellie Jones was at a friend's house in Warrington, Cheshire, when she experienced breathing difficulties at about 3.30am on Saturday.
Paramedics treated her at the scene in Densham Avenue and she was taken to hospital but died shortly before 5am.
An initial post-mortem examination did not reveal the cause of death as the results of further toxicology tests are awaited.
A spokeswoman for Cheshire Constabulary said: "Police investigating the death of a Warrington teenager have arrested three local males on suspicion of supplying drugs and perverting the course of justice. All three males are 16 years of age and are currently assisting with inquiries."
Detectives are trying to piece together her movements last night and warned other youngsters to be mindful of taking illegal substances this weekend.
Superintendent Martin Cleworth, of the Warrington Police Command Team, said: "Our thoughts this morning are with the family and friends of the young girl who lost her life. Specially trained police officers are providing support to them.
"Our investigations into the cause of her death are at an early stage and I would appeal for public help and support in progressing these. I would also like to re-iterate the message, and to young people in particular, around the dangers of taking any illegal substance."
Anyone who has any information for the investigation should contact Warrington Police on the non-emergency number 101, quoting incident number 187. Alternatively, information can be left anonymously on the Crimestoppers hotline 0800 555 111.
Online tributes were paid to Miss Jones. On Twitter, Chloe Ford posted: "She never failed to make someone laugh", while Ruth Ann Collopy said: "Don't think I ever saw her around school without a smile on her face! RIP ell".