Customs officials have found a yacht skippered by a Norwegian man illegally making his way to Antartica.
A spokesman said a plane last night circled the Nilaya and made numerous attempts to hail it but there was no response, and no further sightings since.
At the time of the sighting the Nilaya was in international waters.
The yacht is believed to be under the control of Jarle Andhoy, who made headlines with his companion, Samuel Massie, last February when they attempted to cross the South Pole on quadbikes.
A support yacht, Berserk, was waiting for them in McMurdo Sound but it sank and all three men aboard died.
Mr Andhoy, 35, and Mr Massie, 19, were later rescued from the ice and faced severe criticism for attempting the journey.
On Wednesday, New Zealand authorities said they were looking for Mr Andhoy because it was believed he was embarking on a similar illegal trip, this time aboard Nilaya.
Norwegian authorities had not authorised last year's voyage, or this one, as required by that country's law.
Norwegian newspaper Vestfold Blad yesterday published an interview with Mr Andhoy in which he confirmed he and Mr Massie were on their way to Antarctica.
Mr Andhoy said he needed to find answers about what happened last February.
His friend Stig Hatlo today told Radio New Zealand this morning he had spoken to Mr Anhoy's family overnight (NZT) and his mother said everything was fine on the yacht.
Mr Hatlo did not know Mr Andhoy's exact position and said his friend did not think he was breaking any laws.
"I'm not in a position to tell him that you should not do this, or you should do that, he is very strong guy and it's impossible to tell him what to do or what not to do.''
It takes about 12 to 14 days to sail from New Zealand to Antarctica.
Anyone with updated information on Nilaya's location is asked to contact the Customs service on 0800-428-786.