Auckland police have revealed that the boat that sank in the Hauraki Gulf early on Anzac Day, killing two Devonport children, was custom-made.
Erina Rowles, 8, and her brother Travis, 5, drowned last Wednesday when the 7.3m aluminium craft sank in calm waters off Tarahiki (Shag) Island, east
of Waiheke.
Detective Senior Sergeant Simon Scott said part of the police inquiry was focusing on the history of the boat, which included talking to its former owner and finding out who made it.
Police had spoken to the previous owner, who had been co-operative, he said.
Mr Scott said the boat was made in 1990.
He said he could not speculate on whether its age or a design fault had caused it to sink. "We're looking at all the possibilities.
"It's been described as a custom-made boat by the previous user so that's as far as I can take it.
"He's been very helpful with us in giving us information and that's all going to go into the mix as well.
"I don't think one person's statement is going to, you know, lead you in the direction of what happened. It's going to be everyone's accounts of what they did and what involvement they had in this matter and putting all that together."
Police have revealed that, when inspected, the boat was missing one of drainage plugs that screw into the bottom of the boat.
However, they have not said whether the bung was missing at the time the boat sank.
Other questions remain unanswered, including the theory of the children's father, Lindsay Rowles, that an old anchor rope wrapped itself around the propeller and dragged the boat under the water stern first as he tried to take it towards land.
Asked if police believed they knew what had caused the tragedy, Mr Scott said: "We're not drawing any conclusions at this stage and we haven't completed our investigation."
It could be next week before a cause is revealed.
"The community is very interested in this and we want to make sure we get things right. I think it's too important to be rushed.
"We're not going to put ourselves under any pressure to make any decisions about what happened on that boat. It's pretty important we get it right and we'll take our time."
