KEY POINTS:
Police have named all four people found dead in a burning Christchurch house on Monday.
Police began a murder investigation after determining the fire was deliberately lit.
Four bodies were found in a Puriri St, Riccarton, house about 7.30am on Monday after firefighters were called by a neighbour who saw smoke coming from a window in the two-storey weatherboard house.
Police named two of the victims yesterday, but formal identification of the other two was not completed until this afternoon.
Three of the dead were members of a Japanese family. They were Junichi Tomonaga, aged 58, his wife Keiko, 60, and Mr Tomonaga's mother, Michiko, 80.
A Japanese woman who boarded with the Tomonagas, Kinuko Hanai, 37, was the fourth victim.
Murder inquiry head Detective Inspector Greg Williams said today police were trying to fill a crucial nine-hour gap in the family's movements.
A family friend had visited the Tomonagas for dinner on Sunday and police knew the victims were alive and well up until at least 10.30pm. The Fire Service was called at 7.20am on Monday.
"So our focus is really on what occurred at that house during that time," Mr Williams said.
The first priority for the investigation team was to establish who lit the fire.
Mr Williams said the surviving members of the Tomonaga family -- understood to be two sons and a daughter -- were "distraught" at speculation that the deaths were the result of murder and suicide.
"The investigation team is keeping a very open mind about what occurred here and it would be far too early in the investigation, from the evidence I've seen, to come to any conclusions such as that."
Mr Williams said police now had a "better understanding" about what caused the deaths, but would have to await confirmation through toxicology and other tests. He said that was often the case with fires.
Police said originally the fire had been small, but now termed it "significant".
Scene investigations involving fires invariably took "some time" to complete, Mr Williams said, and a team of 14 experts from police Fire Service and Environmental Science and Research were likely to remain at the house for several more days.
He said it was too early to determine if the offender was from within the family, "or someone who's come to the home".
"We're slowly building up a picture around this family ... to get a deeper understanding of all the dynamics that led up to this tragedy," he said.
Police knew how the fire started but would not comment on the cause.
The fire had caused more damage in the downstairs part of the flat where the Tomonagas and Ms Hanai lived.
Two of the bodies were found in a downstairs bedroom and two in a bedroom upstairs.
Mr Williams declined to say if they were in beds.
He said the results of toxicology tests on the bodies could take some time but he had no evidence to suggest any of the four had been drugged before they died.
Police wanted to hear from anyone who had any dealings with the Tomonaga family, either on a business or social level, or who had visited the house at 95 Puriri St.
"We've got to eliminate who's been in and out of the house," he said.
It was revealed yesterday that the Tomonagas had fallen on hard times after becoming involved with a convicted fraudster in 1998. Mr Tomonaga had been involved in his own tourism business, but was working recently as a driver for a radiator reconditioning company
Police were aware the formerly wealthy family had been facing financial difficulties and had been served notice to vacate their flat.
However, Mr Williams said a family friend had told police they were making preparations to leave.
"The idea that they simply decided to stay there and not move on and commit suicide en masse is, again, speculation at this point in time," he said.
The Tomonagas were understood to have come to New Zealand in the late 1980s and lived in their own suburban Redcliffs home before renting in Puriri St.
They had two sons -- one living overseas and the other believed to live in Christchurch -- and a daughter, Yaeh, 19.
"My understanding, from everyone I've spoken to, is that they were a very likeable family involved in sports and Mr Tomonaga was involved in coaching," Mr Williams said.
"They were a well-respected and liked family."
He said police were "looking seriously" at whether anyone outside the family was involved in their deaths.
"I've made it clear that we haven't closed our minds to what's occurred."
- NZPA
