Police are contacting the families of two Auckland divers missing off Great Barrier Island since last night.
A police spokeswoman said the divers were reported missing from an 8m boat just after midnight.
The police Eagle and Westpac Rescue helicopters searched for the pair without success overnight and an aerial search resumed this morning but has so far been unsuccessful.
The alarm was raised after a diver did not resurface and a second diver who went to investigate also disappeared.
The boat was launched from Whangaparaoa and its occupants were on a free-diving crayfish expedition.
The police spokeswoman said the Wellington-based police national dive squad was due to arrive at the island about 2pm to help with a more thorough search.
Police were contacting the next-of-kin of the divers, who were believed to be from Auckland, she said.
Officers based on the island, northeast of Auckland, were also helping with the search.