Police have launched a homicide probe following a fatal house fire in Auckland's Cockle Bay last month.

Wiremu Arapo, 27, was found dead in the Minerva Terrace home after it caught fire on October 20.

Acting Detective Senior Sergeant Craig Bolton said police made inquiries into the death on behalf of the Coroner - something that is standard procedure - when they discovered the death was suspicious.

"As our inquiries into the circumstances of Mr Arapo's death have progressed, and following a post mortem examination, it has now led police to treat the matter as suspicious."

A team of officers are now working on the case which is being treated as a homicide.

Bolton said two people were injured in the fire and taken to hospital. They have spoken to police.

"I strongly believe there are people that know what has happened to Mr Arapo and I'm urging them to do the right thing and contact us," said Bolton.

"The news of this homicide inquiry may cause some concern to members of the wider community. Police would like to reassure the public that we have a team of committed detectives working on this matter."

The people who lived in the house that burned down had only owned it for six months.

The man who died in the fire had set up a fitness business in the garage of the Minerva Tce, Cockle Bay, home during the country's Covid-19 lockdown, a neighbour
said.

The man died and two others were injured after fire tore through the house shortly before 7pm on October 20.

Paul Pope lives next door to the house and said the people had bought the property about only six months ago so he didn't know them very well.

"They were quiet and kept to themselves. [The man] was running a fitness business from the house after the first lockdown."

Pope was at the gym when the fire began and arrived home to find the street cordoned off.

Geoff Purcell, Counties Manukau Area Commander, said the man who died was found near a doorway.

While the fire was still being investigated on behalf of the coroner, Purcell said he didn't know if the man was trying to leave or get into the house, but there were reports from neighbours of seeing a man trying to get back inside.