A 20-year-old man has died after attending the Electric Picnic music festival in Co Laois.
Paramedics attended the scene at a campsite near the festival site at the Stradbally Hall estate at around 1.45am.
The man was pronounced dead later at Portlaoise Hospital.
Gardai said they were investigating the incident but said there no initial signs that violence was involved.
A post-mortem examination is due to be carried out.
Around 35,000 revellers are attending the popular end of summer three day event.
Festival promoters EP Republic said they had been informed by medics that the dead man had a past heart condition.
"At 1.00am this morning the medics attended a twenty year old male who had collapsed on site," said a spokeswoman.
"He was transferred to Portlaoise General Hospital where he was pronounced dead.
"The medics confirmed that he had a previous cardiac history .
"Our thoughts and sympathies are with the deceased's family and his friends at this very sad time.
"A full investigation is underway."
Organisers later warned revellers about a dodgy batch of ecstasy type pills believed to be circulating at the event.
It is understood some of the drugs were seized by gardai at lunchtime.
A spokeswoman said: "There may be some potentially dodgy 'blue ghost /casper' pills circulating onsite.
"We urge picnickers to be very careful.
The seizure is not believed to be linked to the young man's death in the early hours.