Salavge crews pumping oil from the stricken container vessel Rena have suspended work as strong winds and high swells are forecast.
The ship has been grounded off the coast off Tauranga since 5 October, when it struck the Astrolabe Reef.
Svitzer Salvage captain Drew Shannon says crews are sealing the vessel's tanks and making sure equipment is secure before they leave the area.
He says the weather forecast is for bad weather over the next 24 to 48 hours, including the biggest swells to yet hit the ship.
Mr Shannon says he can't rule out further damage to the boat.
But he says salvors are monitoring Rena and will be on standby in case any more containers fall off.
They are hoping to attach tracking devices to the containers that hold dangerous goods, so they can be found if they float away.
The rough weather will also mean more oil will wash ashore.
Oil clean up continues
On Monday, several clean-up crews were out on the beaches, including Matakana Island, where tar balls have been found in the sand.
Maritime New Zealand says the oiling on the island is probably due to the release of heavy fuel oil from the Rena several days ago.
But it says lighter hydraulic oil still leaking from the vessel appears to be dispersing naturally.
Meanwhile, the agency says it needs people who volunteered to help clean beaches where oil has washed ashore to turn up.
About 7500 people have registered to volunteer in the clean up of Bay of Plenty beaches but just 160 people showed up on Sunday.
National on-scene commander Nick Quinn says if people commit to the volunteer programme they need to turn up to do some of the work.
He says fresh oil could wash up on Papamoa beach on Monday and even if it does not there is still plenty of old oil to clean.
Volunteers are needed on Monday for operations at Papamoa Beach and Maketu Beach.
Oil that spilled from it has contaminated beaches and killed more than 1300 birds.
Milestone reached in removing oil
Earlier, Maritime New Zealand said a significant milestone had been reached, with about 1000 tonnes of oil removed from the ship.
Maritime New Zealand spokesperson Ross Henderson says the salvage teams now face the difficult task of getting the remaining 358 tonnes of oil from a tank that is under water.
He told Morning Report bad weather on Sunday made it too dangerous for divers to continue their work.
He says the process ahead remains very challenging.