Ms Choi was a qualified pharmacist who worked in Miranda. Event goers gather in Sydney Olympic Park Credit:Dominic Lorrimer Assistant Commissioner Frank Mennilli said investigators hoped a post-mortem examination, to be carried out on Sunday afternoon or Monday, would shed light on the type of substance or substances the woman took. "We won't know the full result of the impact and cause of death of this until the autopsy has been conducted," he said, declining to comment on speculation she had taken ecstasy. He said the woman's death was the latest in a string of incidents linked to music festivals, including the death of 19-year-old Georgina Bartter at Harbourlife just over 12 months ago.

"The mentality of drug culture and music festivals - we've got to change it," he said. Police attend to a festivalgoer at Sydney Olympic Park. Credit:Dominic Lorrimer "There's no such thing as safe drugs. There's no such thing as saying you know you can take the drugs and you will be safe. You're playing Russian roulette with your life. You don't know what you're putting into your system." The second woman, a 22-year-old tourist from Britain, has made a satisfactory recovery, he said. She has since been discharged from Westmead Hospital. Mr Mennilli said there was no indication the women were known to each other.

A further nine people were taken to hospital following suspected drug overdoses. All have been released or discharged. More than 120 people were treated from the effects of drugs during the festival at Sydney Olympic Park, and 69 people were charged with possessing and supplying drugs. A further 23 were issued with cannabis cautions. At the same event last year, 221 attendees were charged - although 81,000 had attended, compared with closer to 50,000 this year. Mr Mennilli said the "the situation could have been a lot worse" if not for the presence of more than 400 police officers and 60 medical staff spread across the precinct. But he said it was alarming and disappointing that many revellers continued to ignore messages about the dangers of recreational drug taking.

"It's extremely frustrating. We've been working hand-in-hand with the organisers and promoters and venues to put out numerous messages to try and warn people about the effect of drugs but unfortunately the message does not seem to get through to some people." The event's organisers, Totem Onelove, used social media to express "our deepest condolences to the friends and family of the patron who tragically passed away on Saturday night at Sydney Stereosonic". "As it is a matter with the NSW Police and coroner we cannot make any further statements or comment," the company's post said. A major police operation – involving officers from South West Metropolitan Region, the Dog Unit, Mounted Unit, Public Order and Riot Squad, Traffic and Highway Patrol, and Police Transport Command – was focused on the precinct for a variety of events in numbers thought to be the biggest seen since the Sydney Olympics in 2000. One man who allegedly drilled a hole in a building to try to stash drugs there and another found with 95 tablets were charged last week.

"That's not personal use - that was there to sell," Mr Mennilli said. He said drug manufacturers, dealers and suppliers "don't care" about the potential deadly effects on drug users. "They're there to make money out of other's people misery. They make these tablets and drugs in the backyard, they put impurities in it," he said. "Don't take the drugs, there's better ways of enjoying life, there's better ways of enjoying festivals. You put these things your body, you don't know how you're going to react. "I can honestly tell you that if I had more police dogs and more police, it'd just result in more people being arrested," he said.

Singer Taylor Swift played to a sold out ANZ Stadium in the first Australian show of her 1989 World Tour, while tens of thousands of others revelled in international DJs and producers like Diplo and DJ Snake at the Stereosonic electronic music festival. Also in the precinct was motocross event the Aus-X Open and the Australian Short Course Swimming Championships, bringing the total number of people to an estimated 150,000.