Salvors on board grounded container ship Rena had to temporarily suspend pumping seawater into a submerged fuel tank due to escaping gases.
Maritime New Zealand's salvage unit manager Kenny Crawford said about 750 tonnes of seawater was yesterday being pumped into the submerged No5 starboard tank to enable the remaining 358 tonnes of heavy fuel oil to be brought to the top so it could be pumped to a bunker barge.
However, as the water filled the tank, gases escaped into the alleyway running across the ship aground on a reef off the coast of Tauranga.
Mr Crawford said salvors had to temporarily stop pumping while they vented the fumes escaping from the tank - which took four to five hours - before they could re-enter the corridor and resume pumping. More than 20 salvors were working on board the vessel, said MNZ salvage unit manager Kenny Crawford.
Meanwhile, salvors worked on Rena yesterday, preparing three tonnes of hoses, ladders and two large pumps in preparation for pumping. One of the pumps was reported in position and the other was still to be placed.
The equipment will provide the most level pathway along the corridor and through the hatches for the oil coming out of the No5 starboard tank.
Pumping of the 22 tonnes of lubricants, hydraulic and waste oils from the engine room was being transferred to the barge Awanuia.
Mr Crawford said monitoring of the vessel's hull was continuing with no further significant buckling found.
Underwater transponders had been fixed to four containers known to contain hazardous goods, so they could easily be located should they go overboard. Mr Crawford said the container barge ST60 with two large cranes on board would begin trials this week but efforts to lift containers off Rena would not begin until after the last of the oil had been removed.
Assistant national on scene commander Andrew Berry said systematic sonar sweeps of the seabed to find more sunken containers continued over the weekend and sonar receivers had been attached to some so they were identified for recovery. Several had been found on the seabed within a 1km radius of the ship, but some were in 80m of water.
About 50 containers were yet to be found and that was one of the key reasons why the exclusion zone remained in place, he said.
Specialist container removal company Braemar Howells is continuing to work to remove containers and debris washed up on shore, including from Motiti Island.
Two lightly oiled little blue penguins were recovered from Motiti Island and brought to the Oiled Wildlife Response centre yesterday, taking the total number of birds in care to 403. Mr Berry said all the birds seemed to have coped well with sound from a speedway event nearby on Saturday night.