One man is dead and two people are in a critical condition in hospital after taking drugs at music festival Stereosonic in Adelaide, Australian police say.
A woman died at the same festival in Sydney a week ago, and another man is in hospital in Melbourne.
On Saturday, a 19-year-old man died in hospital after a suspected drug overdose at the festival in Adelaide.
Police have released images of the red or orange pills, stamped with dollar symbols, found in his possession.
They said earlier that a 20-year-old man was taken to hospital on the same day after attending the event.
"It appears as though he also consumed an illicit substance and he remains in a critical but stable condition," a police statement said.
A 21-year-old woman was also in a critical but stable condition "after ingesting an illicit substance", they said.
Both remained in intensive care in hospital.
Superintendent John De Candia said 34 people were refused entry to the Adelaide event after they were found to be carrying drugs. Six people were evicted from the event.
Twenty-three people were issued with drug diversions to attend counselling.
He said police were investigating the man's death and looking to identify the source of the drugs.
"It's hard to say what he had taken. But that is something we will investigate in addition to the other people that are in a critical condition in the Royal Adelaide Hospital," he said.
"I specifically said, before the event, that police did not want to be advising any family of such a tragedy. So this is the worst possible outcome that we could have had on a Sunday morning following the event yesterday."
Further tests would be conducted to determine the make-up of the pills, Mr De Candia said.
"The people that manufacture them make them in backyards, they use a whole range of chemicals used for industrial cleaning, in shocking conditions," he said.
"The people that manufacture them, they are only interested in the profit, they don't care about the consequences.
"They wouldn't care less about what this young man's family is going through this morning and will continue to go through for a very long time."
Stereosonic is an annual festival, held this year in Sydney, Perth, Adelaide, Melbourne and Brisbane on various dates between 28 November and 6 December.
The event's organisers posted a statement on their Facebook page last night confirming the man's death. "Stereosonic is devastated to hear of another loss to drugs," the statement said.
In another post, they warned people attending today's event in Brisbane to "look out for each other".
The death comes a week after 25-year-old Sylvia Choi died at the festival in Sydney of a suspected overdose.
Further disruption in Melbourne
Another man was taken to hospital after an apparent drug overdose at Stereosonic in Melbourne.
Ambulance Victoria said the man, aged in his late teens, was one of six suspected overdoses treated by paramedics at the event on Saturday.
He was taken to hospital in a critical condition but his condition had improved to serious but stable.
The police arrested 70 people at the event in Victoria and seized drugs including ecstasy, MDMA (3,4-methylenedioxy-methamphetamine), amphetamines, cocaine and cannabis.
They said six people were issued with cannabis cautions, two others were expected to be charged on summons with drug offences, and two were charged and bailed.
They also said two festival-goers were expected to be charged on summons with assault, while two others were issued with penalty notices for being drunk.
Problems at 'most major cultural events'
South Australian Network of Drug and Alcohol Services executive officer Michael White said he did not believe the electronic music culture could be held responsible for recent drug overdoses at festivals.
"I don't think there's a culture problem with that type of music," he said.
"I think most of our major cultural events are associated with alcohol or other drugs.
"If you've been to the Grand Prix, if you've been to the AFL, all of those events have an association. Some of them are with alcohol, which has a much higher death rate."
But Mr White said pill testing at music festivals should be considered.
"Whether or not they have a tent where you can go and pick up a pill test and take it away," he said.
"Whether or not you can pick one up from a site before going or whatever. Whatever works. It could be useful."