The family of Reverend Samata Iusitini Leiloa are in mourning after his sudden death while in managed isolation at the Millennium Hotel in Auckland Central.

His was the first death while someone was carrying out the mandatory 14-day managed isolation or quarantine, after arriving from overseas.

Leiloa, a New Zealand citizen, died unexpectedly on Monday after returning from Samoa on Christmas Day.

The 63-year-old died of natural causes and his death had been referred to a coroner, family spokesman Tauanu'u Nick Bakulich said.

Leiloa gained his qualification at Malua Theological College. He is survived by his wife, brother, three sisters and a large extended family.

Hundreds of people posted messages of support for the family on Bakulich's Facebook page.

One person described him as a "jovial soul and character always remembered". Another said they would miss "his encouraging messages and sense of humour".

One person said they were on the same flight to New Zealand and he was well at the time.

Managed Isolation and Quarantine deputy chief Andrew Milne said the death was not Covid related.

"[We are] saddened to confirm that a 63-year-old male, who arrived from the Pacific and is staying at the Grand Millennium Auckland, has sadly passed away.

"The returnee displayed no Covid-19-related symptoms during their previous daily health checks."

Samoa has no transmission of Covid within the community.

Official advice given in a 135-page operations framework for managed isolation and quarantine facilities - when dealing with an unexpected death - shows the heartbreaking reality for those involved.

If the person was staying with other people in the same room, those people would be moved to a different room immediately after the death.

Authorities have not said whether or not the man who died yesterday had been self-isolating with anyone else.

The document also reveals that every unexpected death in a quarantine facility is to be treated as a Covid-related death - even if the death appears to be unrelated to the virus.

"Staff should wear (personal protective equipment) and the body and room should be treated as if the person had been infected with Covid-19 prior to their death."

text by Amy Wiggins and Vaimoana Tapaleao, NZ Herald