Police have blamed the death of a 25-year-old Sydney woman at an electronic music festival in Sydney on a drug overdose.

Another woman, 22, is in an induced coma in hospital after going to the Stereosonic festival, where almost 70 people were charged with drug offences.

The 25-year-old, from Oyster Bay, was taken from the festival to Concord Hospital, where she later died.

"It's been reported at this time a 25-year-old woman has lost her life and we believe is a direct result of a drug overdose," Assistant Commissioner Frank Mennilli said.

"We won't know the full extent of the situation until an autopsy has been conducted and investigators are now preparing a brief for the coroner."

The 22-year-old, believed to be from the UK, is in a serious but stable condition in Westmead Hospital.

The organisers of the event have expressed their sympathies to the family of the woman who died.

"Totem Onelove conveys our deepest condolences to the friends and family of the patron who tragically passed away on Saturday night at Sydney Stereosonic," a spokesperson said.

"We appeal to our audience that they stay safe and look out for each other."

The organiser said it was now a matter for police and the coroner.

Drugs charges against 69 festival goers

A police sniffer dog operation on festival goers saw 62 people issued with drug possession court notices, while seven were charged with drug supply notices.

Of those set to attend court, 57 were charged with possessing MDMA (the active element in ecstasy pills), two for cocaine, two for other restricted substances, and one for LSD, or acid, police said.

Cannabis cautions were issued to 23 people.

Officers said they had warned people at the festival about the dangers of drug use.

Police said the number of arrests was alarming and that they were disappointed with the behaviour of many of the 50,000 people who were at the event at Sydney Olympic Park.

"This number is alarming and disappointing, especially after we warned revellers about the dangers of drug use," Assistant Commissioner Mennilli said.

Police said they had mounted a major operation in a bid to ensure the festival was a safe and secure event.

Two men were found earlier in the week allegedly trying to drill holes in buildings at the site to hide drugs, before fences were installed and the park went into "lockdown".