Maritime New Zealand says a small amount of oil is leaking from the stranded container ship Rena.
The vessel struck Astrolabe Reef off the Tauranga coast on 5 October last year. Tonnes of oil and container debris have polluted beaches in the region.
Maritime New Zealand said on Tuesday that oil is again leaking into the sea, but it is unlikely to be a lot as only small amounts remain on the ship in different areas.
The authority says oil may reach the Coromandel region overnight.
About 10 containers have washed out to sea after a cover securing a hold on the bow section was dislodged during rough weather on Tuesday.
Salvage efforts are on hold until weather conditions improve.