Salvage teams are preparing to pump the last fuel oil off the stricken ship Rena after they were forced to stop work because of noxious gases yesterday.
Salvors have been pumping seawater into the ship's submerged starboard tank through the deck to raise 358 tonnes of oil to the top of the tank, where it can be pumped out.
Maritime New Zealand assistant national on-scene commander Andrew Berry said work was halted for five hours yesterday morning because of the noxious fumes coming from the tank.
"The air coming out of the top of that tank had some hazardous fumes in it. They've vented that area yesterday and then been able to continue work yesterday afternoon," he told Radio New Zealand.
More than 20 salvors were on board yesterday to prepare the three tonnes of hoses, ladders and two large pumps needed for the operation.
One of the pumps was in position and the other was still to be placed.
Salvage teams pumped 22 tonnes of lubricating oil out of the Rena's engine room onto the barge Awanuia yesterday.
The ship's hull continued to be monitored and no further significant buckling was found yesterday.
Sonar scans of the seabed are continuing to locate more of the 88 containers which fell off the Rena in a storm three weeks ago.
Thirty-two have been found, several on the seabed within 1km of the ship, but 56 were still unaccounted for.
Mr Berry said it was like "looking for a needle in a haystack".
"The first step is to find them, and then they will use cranes and barges to recover them off the sea floor."
Underwater transponders have also been fixed to four containers known to contain hazardous goods so they can be tracked if they are lost overboard.
A crane barge from Australia has arrived but efforts to lift containers off the Rena will not begin until after the last of the oil has been removed.
Two volunteer beach clean-ups at Maketu and Papamoa are scheduled today.
The oiled wildlife facility was caring for 403 birds last night, including three oiled birds which were yet to be washed.