The Department of Conservation is responding to reports of equipment bouys, ropes and seabirds with potential oil on them.
Maritime New Zealand is leading the response, with the assistance of the Department of Conservation and local iwi.
Maritime NZ Incident Controller Bruce Barton told 1 NEWS they were notified of "a small marine oil spill" on Monday by a fishing vessel operating in the area of the Manawataawhi (Three Kings Islands).
"The vessel advised of some oil being seen on fishing gear and on a small number of sea birds in the immediate vicinity," Mr Barton said.
Weather in the area was poor and communications with the vessel was intermittent and of poor quality, he added. The weather remains poor, meaning a planned helicopter flight for today has been cancelled.
"It will occur as soon as the weather allows for safe operations," Mr Barton said. "The immediate focus is on establishing reliable information about the spill in terms of its location, volume and potential impacts.
"As soon as the notification was received, activity began to try to determine the extent of the oil spill and any actual or potential impacts.
Yesterday, a Royal New Zealand Air Force C130 Hercules operating nearby on another task was able to fly over the area. The crew reported some possible small amounts of oiling on the shores of one of the islands in the group.
Today, Maritime NZ is requesting the NZ Defence Force to fly an aerial reconnaissance flight to obtain images that will provide key information, Mr Barton said.
"In addition, Maritime NZ is making preparations, including around oiled wildlife, for any possible response that may be required; it is too early at this stage to know what, if any, level of response might be required," Mr Barton said.
Work is also underway to attempt to establish the origins of the spill, he said.
A DOC spokeswoman told 1 NEWS it might just be a "little oil flick" from passing boats, but DOC is taking the reports very seriously.
"At this stage there are only reports of oiled equipment and wildlife and no evidence of oil spill or slick," she said.
Ngāti Kuri spokesman Harry Burkhardt told 1 NEWS "it’s early days and they are trying to understand the cause or extent".
He said Three Kings Islands is an area "they are trying to protect for future generations". The iwi's focus is working out what impact the potential oil spill may have on local wildlife, especially seabirds, he said.
There are concerns the capacity to clean the spill is far away; from Mr Burkhardt’s memory, the closest dedicated oil spill kit is in Whāngārei.
Scientific experts are supporting research efforts, including The Seabirds Trust’s Chris Gaskin.