A 26-year-old man attending a dance music festival in western Sydney fell unconscious and died on Saturday, two years after another death at the same event.
The man, from Albury, was among thousands of revellers at the Defqon.1 music festival at Sydney International Regatta Centre in Penrith.
The man's friends administered first aid until NSW Ambulance paramedics arrived and he was taken to Nepean Hospital, where he later died.
Police are yet to identify the man.
Nine more festival-goers were reportedly taken to hospital as well.
"A man was located unconscious at the Defqon.1 festival at about 11.30 last night. He was taken to Nepean Hospital where he was pronounced deceased a short time later," a police spokesperson said.
An investigation is under way and witnesses will be interviewed by Penrith detectives. They are appealing for anyone with information to contact Penrith police.
Investigators will prepare a report for the NSW Coroner.
The death comes after James Munro, 23, died of a suspected ecstasy overdose at the Defqon.1 festival in 2013. Mr Munro told paramedics he had taken three pills, which he believed to be ecstasy, before he suffered a series of cardiac arrests.
The festival organiser, Q-dance Australia, said in a statement it was fully supporting the police investigation into the Albury man's death.
The festival organiser, Q-dance Australia, said in a statement it was giving the police investigation its full support.
"Our thoughts and prayers are with the man's family and friends," it said.
"Everyone on our team is deeply shocked and affected by this tragic event."
Police arrested 60 people at the festival: 46 arrests were for drug offences, four of which were for drug supply, with two people allegedly caught with 46 pills, believed to be MDMA.
Others arrested were charged with public order and trespass offences.
Defqon.1 offered both overnight camping tickets and day passes and ran from 11am on Friday with the latest checkout at 1pm on Sunday.
"Our thoughts and prayers are with his family and friends," Q-dance Australia said.
"Everyone on our team is deeply shocked and affected by this tragic event."
In a related operation, a bus heading to the festival was stopped on Sherbrook Road at Hornsby by officers from Ku-ring-gai Local Area Command.
More than 30 passengers were searched with 14 allegedly found to be in possession of drugs including MDMA and cannabis.
Following this stop, a search warrant was executed at a home in Cecil Road, Hornsby.
Police allegedly found white powder suspected of being cocaine as well as pills, believed to be MDMA, steroids and $5800 in cash.
The man's death is not the first time tragedy has hit the dance music festival.
In 2013, a 23-year-old Victorian man passed out and died at Nepean Hospital from a suspected overdose.
At the time Detective Inspector Grant Healy, of Penrith police, said the drugs reportedly included "magic mushrooms, cannabis, amphetamines, cocaine, LSD, what people were reporting to be ecstasy [and] some GHB".
