Calm weather around the grounded container ship Rena is helping salvors set up a system to pump heavy fuel oil from a submerged tank.
Up to 150 metres of hose, two large pumps and up to 40 metres of ladders are being installed to guide a path for about 360 tonnes of oil to travel from the fuel tank to a bunker barge.
As much as 750 tonnes of seawater are being pumped into the starboard tank so the heavy fuel oil will float to the top, from where it can be taken out.
Maritime New Zealand's Andrew Berry told Morning Report the so-called hot tapping technique does not require any heating of the oil.
Delays on Sunday were caused by hazardous fumes coming from inside the tank on the ship, which has been stranded on Astrolabe Reef near Tauranga since 5 October.
Mr Berry also said missing containers from the Rena would be recovered from the sea floor using cranes and barges. Fifty-six containers from the ship are still to be found.
A large number of the 88 containers lost overboard during rough weather were located in sonar searches during the weekend, Mr Berry said.
About 30 containers have either come ashore or have been recovered from the seabed, while some have sunk to the sea floor. The authority does not know where the rest are.
Underwater transponders have been fixed to four hazardous goods containers still on the Rena, so they can be found easily if they fall overboard.