SALVAGE team confirmed that oil pumping from the MSC-chartered 3,300-TEU Rena that ran aground off New Zealand's north island has passed halfway.

A total of 645 tonnes of fuel oil was confirmed to be transferred to the tanker Awanuia, according to an update from New Zealand Bay of Plenty Regional Council. When Rena was stranded on the Astrolabe Reef on October 5, there was around 1,700 tonnes of fuel oil on the ship, and 350 tonnes has leaked out of the ship so far.

Maritime New Zealand Salvage Unit Manager Bruce Anderson said it was encouraging to see the oil pumping work pass the halfway point, but warned the second half of the fuel posed some serious challenges.

He said: "The salvors now have the pumping system working well and they are getting good transfer rates, which is excellent.

"However, the second half of the oil is in around four tanks, rather than one - and one of them is submerged underwater."

Mr Anderson said the salvors would establish a fuel transfer system from the three tanks in the engine room, which together hold around 250 tonnes of oil, to the tug Go Canopus.

"Transferring the oil direct to Go Canopus will hopefully speed up the process."

Also, national on scene commander Rob Service said they are preparing a contingency plan "in case the remnants of the 5-10 tonnes of oil released from the ship overnight on October 22/23 reached Tuhua/Mayor Island or the Coromandel (Peninsula)."

A wildlife stabilisation site had been set up on the Tuhua/Mayor island and a team has been sent to assess the feasibility of using booms to protect key areas, as well as to see how the wildlife there will be affected if there is any oil reaching the shore later.