The Mutiny Festival in Portsmouth has been cancelled after an 18-year-old woman and a 20-year-old man died after falling ill on Saturday evening.
The deaths are being treated as separate incidents and are not being treated as suspicious, however Hampshire Constabulary said inquiries are being made to determine the circumstances.
Two others remain in hospital and 15 people also needed treatment.
The festival issued a “harm prevention alert” via social media on Saturday night but on Sunday cancelled the event entirely a day early due to safety fears.
Ready for the paint party! 🦄 pic.twitter.com/M4tqbRoB8k— Mutiny Festivals (@MutinyFestivals) May 26, 2018
Dizzee Rascal, Craig David and Sean Paul top the bill at the two-day event that ends on Sunday.
Police were first alerted to the woman falling ill at the site on Saturday evening and the man was found collapsed around 20 minutes later.
Both were taken to the Queen Alexandra Hospital where they later died.
In an earlier statement, the festival said it was “devastated to hear of the tragic loss of life from its festival family”.
But on Sunday morning, it said the decision had been taken to cancel the final day as a “safety precaution”.
The festival said: “Following the terrible news from earlier today, the team behind Mutiny Festival are incredibly sad to announce that the Sunday of the festival has been cancelled as a safety precaution.
“The safety of our amazing customers has always been paramount to us and so to keep everyone safe and in respect to those who have passed, we have taken the decision not to open today. As you can imagine, this decision was not taken lightly and was taken with the support of the local statutory authorities who we continue to work with.
“Enquiries are being made into the circumstances of what has happened, but we must reiterate our advice to all our customers to responsibly dispose of any substances.
“More information will follow when available, we appreciate your understanding at this difficult time.”
Local MP Penny Mordaunt tweeted that the two people “died after taking drugs”.
In a message posted on social media after the pair were taken ill, organisers warned of a dangerous substance circulating on site and urged revellers not to take anything.
“The deaths are being treated as separate incidents at this stage. They are not being treated as suspicious but inquiries are being made to determine the circumstances of what happened in each case.”
The force said next-of-kin for both the woman and the man had been informed and were being supported by specialist officers.
Anyone with information is asked to contact police on 101.
Hampshire Police last year called for anybody under the age of 18 to be banned from attending the Mutiny Festival after reports of drug-use and violence.