A 16-year-old boy who was arrested after a girl of the same age died having taken a tablet containing an unknown substance has been released on bail.
Police held the teenager on suspicion of supplying a class A drug, such as ecstasy or LSD.
Officers were called to Move nightclub in Exeter shortly after midnight, after staff raised concerns about the 16-year-old.
She was taken to Royal Devon and Exeter Hospital, where she died.
Her next-of-kin have been informed and are being supported, the force said.
A number of teenagers are thought to have taken the tablets, and anyone who may have been affected has been asked to come forward.
The boy, from the Exmouth area, was arrested yesterday and released on police bail to return on 2 March.
Detective Chief Inspector Lee Nattrass said: "We have identified several teenagers already who reported that they had taken drugs, but we would urge anyone else who has felt unwell as a result to seek medical help and to contact us.
"We have seen time and time again that these substances can kill, and we have another tragic case on our hands.
"Talk To Frank is a website that has vital information for people about many types of drugs, and we ask that parents have open and honest conversations with their children about the risks of drugs.
"You don't know what they contain, and you don't know the reaction you may have - it could be fatal.
"I urge anyone considering taking drugs to think twice and reconsider."