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.