Jake Hayes, Toni Maree Johnston and Connor Swetman all died in a house fire in Hamilton.
Three young people killed in a tragic Hamilton house fire in November 2014 died from soot and smoke inhalation, the coroner has ruled.
Toni Maree Johnston, 23, Jake Lindsay Hayes, 19, and Connor James Swetman, 17, all died in the blaze at a house party in Collingwood St just before 5am.
Coroner Gordon Matenga has praised the "selfless and courageous" actions of two heroes who undoubtedly saved other people's lives in the fatal blaze.
Thirty-two people had attended the party, which had been organised by Hayes.
The house had smoke alarms but they were not being used, the coroner said.
The three victims were all found to have high levels of between 49 per cent and 52 per cent of carbon monoxide saturation, which is considered to be lethal and all suffered significant burns to their bodies.
The inquest findings, released today, say the fire started on a couch in the downstairs lounge of the villa, while the victims were in the rooms upstairs, but the cause of the fire still remains a mystery.
"The cause of the fire could not be determined as either a deliberate act or an incidental ignition," Matenga said.
The coroner praised two people for rescuing others when the blaze broke out. Matenga said he was struck by the "enormity and peril" of the situation they faced.
Jesse Tudor awoke to find the house on fire and ran upstairs to warn people who were asleep. The coroner said this bravery saved five people's lives, including his friend Joseph Soutar who he woke up.
Tudor had later tried to re-enter the house but was blown back by the force of the fire's backdraft.
Joseph Soutar had carried one woman out of his burning room and had alerted others still inside.
Coroner Matenga said the two men's actions were "selfless and courageous" and he planned to nominate them for bravery awards.
Tudor was in custody and appeared surrounded by four Corrections Department staff at the time of the inquest in February.
Toni Johnston's brother Greg told the Herald it was hard not knowing a definitive cause of the fire, but it did not change the fact they had lost Toni.
"Toughest thing I found was sitting and listening to the blatant inconsistencies in the statements of certain witnesses at the inquest, without them facing any follow-on consequences."
At one point in the hearing, the coroner halted proceedings to allow one witness to get legal advice after he changed his evidence about when he left the party.
"As the case remains open, I hope that people who may have further information for the police have the courage to come forward - for the sake of those lost and their families and friends."