A New Zealand detainee has died at Sydney's Villawood Immigration Detention Centre.
Staff and paramedics tried to resuscitate the unconscious 42-year-old on Monday night, but he could not be revived.
He is suspected to have suffered a heart attack, the department of immigration said.
He has been named in the media as Robert Peihopa, however NSW police declined to confirm his name or his nationality.
"The Department expresses its sympathy to the family of the deceased man and will cooperate fully with the NSW Coroner who will prepare a report on the death," the Department of Immigration said in a statement.
"As this matter is now subject to a coronial inquiry the Department will not be commenting further at this time."
Opposition Immigration spokesman Richard Marles told the ABC Labor has called for the Government to investigate the incident so the cause of death could be determined.
"Immigration Minister Peter Dutton needs to provide an assurance to the Australian community that there are no security concerns following this incident at the Villawood facility," he said.
Last month New Zealand Prime Minister John Key met with his Australian counterpart, Malcolm Turnbull, amid news New Zealanders were being stripped of their visas at a rate of one a day.
Fellow New Zealand detainee Vaelua Lagaaia said Peihopa had spent about 10 months in detention and was a fit and healthy man.
"So it came as a surprise that he had a heart attack," he told New Zealand website stuff.co.nz.
"We went up to the compound where his body was. His body was covered with a blanket. They had NSW Police here and [detention centre contractor] Serco, and Border Force.
"They gave us an opportunity to say goodbye to the bro, which we did."
Authorities allowed Kiwi detainees to do a haka as Peihopa's body was carried out, he said.
New Zealand MP Kelvin Davis said he would continue looking into the issue and supporting those Kiwis in Australian detention centres.
"The sad thing is that there's a family now who are mourning their loved one in Aussie, and there will be family back in New Zealand," he said.
"Remember, these guys are detainees, they're not prisoners, they're no longer criminals, they're in a detention centre just pending the outcome of their visas – to me it's just tragic all around."
It was also reported that the New Zealand High Commission in Canberra has been notified of the death.