The news is good for wildlife near the Three Kings Islands, as investigations suggest an oil spill in the area is smaller than originally feared.
A fishing vessel alerted Maritime NZ on Monday after it found oil on fishing gear and sea birds while close to the islands, which are north of Cape Reinga.
A Maritime NZ spokesman said it was unclear whether the oil had come from a boat or a drilling operation.
But it appeared the spill was much smaller than originally thought, he said.
The immediate focus was on getting reliable information about the size and impact of the spill, Maritime NZ's incident controller Bruce Barton said in a statement.