Radio New Zealand Pacific reports that the group which included Bougainville Health Minister Charry Napto and his wife and son, left Buka for Nissan late morning last Saturday.
But they never arrived on the outer island.
A survivor reached shore and has been able to tell officials about the sudden sinking of the banana boat, but the head of the Disaster Office, Lieutenant Colonel John Imaka, says, despite a wide search by aircraft and boats, nothing has been found.
But he says they will continue to search in the waters toward New Britain and the Papua New Guinea mainland.
Meanwhile there are further calls for the government to do something about providing adequate shipping to the atolls.
Most often people travelling to the outer islands are forced to use banana boats which are not designed for the open sea and struggle if the water is rough.
Tulele Peisa's Ursula Rakova has been pushing for an improved service for years.
Now the North Bougainville women's MP, Amanda Masono, has added her voice. She says both her late father, Raymond Masono, and Napto had been calling for a proper service, and she has now joined the call.