Maritime New Zealand has spoken of the frustration being felt by salvors who are trying to pump out the last fuel tank of oil on the container ship Rena.
It has been over a week since any heavy fuel oil has been pumped from the ship stranded off Tauranga.
About 750 tonnes of seawater has had to be pumped into the starboard No 5 tank so the remaining 350 tonnes of oil will rise to the top.
When pumping from the tank began earlier in the week, salvors found air pockets inside that needed to be purged.
Maritime New Zealand's salvage adviser Captain John Walker says the salvors are frustrated, and furious, that they cannot get the oil off, but are constantly trying to find a solution.