The 23-year-old man and 21-year-old woman died in Nepean Hospital a short time later, while a fourth person - a 26-year-old woman from Jamisontown - remains there in a critical condition.
New South Wales Premier Gladys Berejiklian has now vowed to shut the entire Defqon.1 festival down. People always have and probably always will take drugs.
"I never want to see this event held in Sydney or New South Wales ever again - we will do everything we can to shut this down", she explained in a press conference.
Four people have now died at the Defqon.1 dance festival in Sydney in the last five years.
Two people have died and three others are fighting for life in hospital after attending the Defqon.1 music festival.
She said: "I'm absolutely aghast at what has occurred, I don't want any family to go through the tragedy that some families are waking up to this morning, it's just disgusting to think about".
"What we can't do is be in people's heads, be in people's decision-making processes when they decide to take illicit drugs".
Acting assistant commissioner Allan Sicard said on Sunday more than 180 police including 20 detectives worked throughout the festival.More news: Steelers imploding as WR Antonio Brown doesn't show up to Monday's practice
Of those, ten were charged with dealing, including two 17-year-old girls who police allege got 120 capsules into the venue by smuggling them in "internally".
Festival organisers expressed their condolences for the victims' families this morning.
Harm minimisation group Sniff Off said it was "disgusting" Ms Berejiklian was "using the tragic loss of these two young lives to push her absurd "just don't do drugs" message, when it is the NSW government's extreme overpolicing measures that allowed deaths like this to occur in the first place". It has since offered its "thoughts and prayers" to the suspected drug victims.
"If drugs are found, you will be handed over to the police", the festival said in a statement on its website.
An investigation is now underway into the circumstances surrounding the man and woman's deaths with officers from Nepean Police Area Command appealing for anyone with information about their deaths to come forward. Festival organisers are working closely and co-operating with the authorities regarding the fatalities and the number of medical presentations made during the evening, a full investigation is now underway.
A 33-year-old man from Mt Pritchard was also charged with supplying a commercial quantity of a prohibited drug after he was allegedly found with MDMA, while a 27-year-old man from Sydney was charged with supplying a commercial quantity of a prohibited drug.
Unharm posted: "For years Defqon.1 has had a "zero tolerance" policy on drugs".