Christchurch police insist they did everything they could to protect the house where the bodies of two women were found from arson.
The Wainoni property beneath which the bodies of Rebecca Somerville and Tisha Lowry were buried was severely damaged in a suspected arson attack on Saturday night.
Inspector Dave Lawry says police went beyond the call of duty by advising the owners and the company that secured the mortgage that arson had been threatened, and keeping a guard there for two days after the scene examination was complete to give the owners time to arrange security.
The fire service was also advised of the threat, and police and community patrols ordered to watch the property.
Inspector Lawry says the owner of the adjoining house, Jason Hall, elected to do nothing to protect his property.
Mr Hall says the police are paid to protect the community and he's insulted they say he should have taken responsibility for his property.
Meanwhile, police say all evidence had been gathered from the property and nothing was lost in the fire.
Christchurch City Council is rejecting responsibility for the fire.
The former mayor of Masterton, Bob Francis, says he took effective action to prevent arson after seven people were murdered in his town in 1992, and he can't believe Christchurch did not do the same.
He says arson attacks endanger neighbours as well as firefighters.
But a senior executive at the Christchurch City Council, Anne Columbus, says the owners of the Wainoni road house had a responsibility, as well as the council.
But she says even so, the council would have provided more protection if talk of arson had been credible.
Crime scene fires act as cleansing ritual - fire officer
A fire safety officer says torching houses where horrific crimes have happened can act as a cleansing ritual for some members of the community.
Ray Coleman of the Fire Service in Auckland told Nine to Noon he does not believe prosecution would deter people from burning down such places.
Mr Coleman also said he is not aware of anyone being prosecuted in the past.
Auckland University arson expert Ian Lambie says these actions are deeply rooted in culture.
He says people used to burn witches to destroy so-called evil, and these days view crime houses in a similar light.
Trend must stop - Newbold
Canterbury University sociologist Greg Newbold says setting fire to houses connected with horrific crimes is becoming a trend that must stop.
There were also fires following the Aramoana and Bain family killings in 1990 and 1994.
Dr Newbold told Morning Report that burning down a crime scene before a trial destroys evidence that could be essential, especially if a case drags on for some time.
He says such fires are arson if they have not been approved by the police, and must be treated as such.
The bodies of Rebecca Somerville, 35, and Tisha Lowry, 28, were found beneath the floor of the Christchurch house on 4 September.
Mrs Somerville's husband, Jason Somerville, is accused of murdering her last month and Ms Lowry in September last year. Their funerals were held on 12 September.