A small amount of oil is leaking from the wreck of the Rena off the Bay of Plenty coast.
Maritime New Zealand (MNZ) is warning of the possibility some oil could wash up on beaches in the next few days, but said the leak was unlikely to have a significant impact.
It was not known how much oil had leaked in the latest incident.
Only some tens of tonnes of oil were left on the ship, in pockets around the wreck, and it was very unlikely all of it would be released in one event, MNZ said.
The oil could reach the Coromandel overnight. If it did, it was expected to be as a light sprinkling on shorelines between Whiritoa and Whitianga.
"It is unlikely to have a significant impact – however, it is important people are aware there could be some oil on their beaches over the next few days."
Waikato Regional Council staff would check potentially affected shorelines tomorrow.
About 10 more containers are estimated to have fallen into the sea as heavy swells battered the fragile wreck today.
MNZ said swells of up to 7m forced a hatch cover off the number three hold in the bow section of the stricken ship, letting the containers fall into the sea.
Bad weather two weeks ago had already dislodged a number of containers, wooden debris and oil, and response and recovery manager David Billington said the loss was not unexpected.
The ship has been in a fragile state for some time.
Much of the stern was sitting beneath the water after the Rena snapped in half on January 9, three months after it struck a reef off the Tauranga coast last October.
Billington said one container was seen floating near the wreck. It was possible the others had sunk to the seabed.
No salvage operations would take place during the rough weather, but salvage and container recovery teams were ready to respond as soon as weather conditions allowed.
Heavy seas were forecast to ease tomorrow.
MNZ said about 649 containers were accounted for onshore, of which 575 had been removed from the Rena, and about 74 retrieved from the sea and shoreline.
- Fairfax Media