The owners of a historic vessel that sank in Auckland's harbour say the conditions for the event were "unusual" and hope an investigation will provide answers.
The 111-year-old ferry Kestrel suddenly sank at its Wynyard Wharf berth on Tuesday morning.
Its owners, the Kestrel Restoration Society, on Monday said parts of the sinking still didn't make sense.
Society chairman Mike Alston said an alarm on the ship had not gone off despite being proved to work earlier.
"We test it and it's used regularly ... that's unusual and warrants investigation, but beyond that we don't have other evidence," he said.
He said police would be looking for CCTV footage around the site as part of the inquiry into the sinking.
Half the ship had been pulled up in pieces but the hull still remained at the bottom of the Waitemata Harbour while insurance assessors figure out what to do with it, he said.
The hull was being held down by the engine but the 170-tonne weight meant any crane capable of lifting it would be too heavy for the wharf.
Mr Alston previously told NZ Newswire foul play was not suspected by possible.
"If someone caused the Kestrel to sink, it could be another vessel hitting it, they will be going for them for that cost," he said.
The Kestrel had been the last of about 30 double-ended Waitemata Harbour ferries still afloat and had spent more than a century transporting passengers.
The society had been planning to restore the vessel to working order.
The vessel, which had been pulled up for repairs a few years ago, was insured for recovery of the wreckage, but not to be restored to its original condition.