Maritime New Zealand says its investigation into a collision that resulted in an anti-whaling boat sinking is proving complicated, because it involves a diplomatic element.
The Sea Shepherd Conservation Society's trimaran, the Ady Gil, was in a collision with a ship from a Japanese whaling fleet in Antarctica in January. It sank while being towed.
The craft was previously the New Zealand Earthrace and was skippered by New Zealander Peter Bethune.
Maritime New Zealand is leading the investigation along with several agencies, including the Transport Accident Investigation Commission.
A spokesperson for Maritime New Zealand says the remote location of the incident and the number of parties involved makes for a complicated investigation process.
The spokesperson says it did manage to interview Mr Bethune before he boarded a Japanese whaler that is now taking him to Tokyo for questioning.
The organisation says all parties involved are co-operating, but could not say how long the investigation would take to complete.
Facing prosecution
A team of lawyers hired by Sea Shepherd is waiting to defend Mr Bethune, who is facing prosecution in Japan.
He boarded the Shonan Maru II three weeks ago, after the Ady Gil sank.
The Shonan Maru II is due to arrive in Tokyo in the middle of the month. Japan's foreign minister says he will be handed over to the coastguard and prosecution is likely.
Mr Bethune's wife, Sharyn, says Sea Shepherd has hired five highly qualified lawyers to represent him.
She says Japanese officials are trying to stifle adverse publicity by preventing her husband talking to anyone who is not on the Shonan Maru II. She is not worried about his wellbeing.
The Government says Mr Bethune is receiving full consular support.
Foreign Affairs Minister Murray McCully says he has spoken to Mr Bethune and the Japanese government and proper process will be followed.
