Pumping of heavy fuel oil off the stricken container ship Rena has temporarily paused following four days of continuous pumping.

Maritime New Zealand says pumping from the submerged number five starboard tank has stopped after salvors reached the interface between the oil and water in the tank, and began pumping seawater.

Awanuia and Go Canopus recieve oil from Rena on Astolabe Reef.

MNZ salvage unit manager Arthur Jobard says the pumping process was reaching it's final stages, and was slowing down.

'The salvors have reached the point in the tank where the oil and water meet. They have suspended pumping to allow more oil to float to the surface and will resume pumping later on today.

'It's a matter of being patient and allowing the oil to rise to the surface so it can be extracted."

So far approximately 225 tonnes of the 358 tonnes of heavy fuel oil has been pumped off, at an overall rate of four tonnes an hour.

Arthur says work is continuing to strip the remaining accessible oil in other parts of the ship including the residual oil from the port number 5 tank.

The port number 5 tank held 772 tonnes of heavy fuel oil when Rena grounded on October 5. Salvors ceased pumping oil from this tank on October 27, leaving only remnants of oil.

Arthur says as part of the "stripping" process, salvors were now revisiting this tank to remove the last few tonnes.

MNZ National On Scene Commander Rob Service says shoreline assessment and clean-up was continuing around the Bay of Plenty.

Wildlife night operations teams were out last night patrolling Mount Maunganui for oiled little blue penguinsand National Oiled Wildlife Response Team Coordinator Helen McConnell says teams targeted the birds' burrows.

"Our night patrol teams have been finding very few oiled penguins coming ashore. Last night they went out to check whether there were oiled birds in the burrows to make sure we weren't missing any.

"The good news is they checked 65 little blue penguins and collected only one oiled penguin."

Helen says the team identified some oiling on Leisure Island, which could affect the penguin population there. Shoreline clean-up assessment teams were following up on these reports today.