An investigation has been launched into how a propeller came away from an Interislander ferry during its Cook Strait crossing on Tuesday night.
It is the third time that the Transport Accident Investigation Commission has investigated problems with the Aratere.
The ferry was on its 6.30pm sailing from Picton when a crack in its shaft caused a propeller to come away mid-crossing. The ship continued to Wellington on one engine.
The chief investigator for the Transport Accident Investigation Commission, Tim Burfoot, says losing a propeller at sea is extremely rare and the commission has launched an urgent inquiry into how it happened.
The Aratere underwent a $53 million refurbishment in 2011 which included installing new propellers but just months later was out of action for two weeks following major engine failure.
The troubled ferry was pulled from service in May this year when its radar system failed and the starboard stabiliser needed repairing.
KiwiRail chief executive Jim Quinn said that the problems are in no way linked and there was no danger to passengers and crew on Tuesday.
Chief executive Jim Quinn told Radio New Zealand's Checkpoint programme on Wednesday that it is unusual for a propeller to break, and he would expect they should last as long as the ship. He said the ferry could sail easily on one propeller.
Transport Minister Gerry Brownlee said he does not know if the refurbishment had anything to do with the breakdown.
"It is serious and we do want to know what's happening, so the Transport Accident Investigation Commission are on the job, as are KiwiRail. I would expect that in the next day or so a little clearer picture will emerge about what actually happened."
Travellers are being rebooked on the Arahura, which has now taken up the Aratere's timetable.