Salvors aboard the Rena have all but finished removing oil from the stranded cargo ship and are now shifting their focus to its cargo.
Maritime New Zealand's Salvage Unit Manager Arthur Jobard says about 290 tonnes of oil has been pumped from the Rena's number five starboard tank.
He says there is probably about 60 tonnes of oil still on board which will be removed manually as it floats to the top of the water in the tank.
National On Scene Commander Mick Courtnell says the Rena could still cause a serious oil spill.
He says there's still a threat from an unknown amount of oil trapped in the duct keel and staff are on standby to deal with that if, and when, it's released.
Mr Courtnell says the crane ship ST60 will move alongside the ship on Monday to begin removing the 1280 containers it is carrying.
However, Transport Minister Steven Joyce says it can only remove about six containers a day, so it could take longer than seven months for all the cargo to be removed.
Mr Joyce says two are holding the dangerous substance ferro silicon, and are sitting below deck.
He says the Rena could still break up in bad weather.
Mr Joyce says Maritime New Zealand has told the ship's owners they must remove the wreck once the containers have been recovered, because it is a shipping hazard.
The Rena was carrying 1368 containers when it ran aground on the Astrolabe reef off the coast of Tauranga on 5 October. Eighty-eight have since been lost overboard.