Teams work to salvage more Rena debris

Small amounts of oil are washing up on the coast of Mt Maunganui after wild weather caused further damage to the stricken ship Rena.

Maritime New Zealand said recovery teams were working to pull debris out of the sea, as small droplets of "possibly new" oil was found washing up on the coast between Mt Maunganui and Omanu.

The Astrolabe Reef was hammered with swells of up to six meters on Wednesday night, which reduced the list of the ship's stern and sent an unknown quantity of oil, wooden debris and containers overboard.

Maritime New Zealand's response and recovery manager David Billington said there was also further damage to the bulk heads at the front of the stern section and the forward section of the ship.

The movement and deterioration of the ship was not unexpected, he said.

Much of the stern was sitting beneath the water after the Rena snapped in half on January 9, three months after it struck the reef off the Tauranga coast in October last year.

Salvors, a recovery team and a shoreline clean-up team were now working to clean the oil and debris out of the sea and assess the full extent of the damage done to the Rena.

Maritime NZ national commander Rob Service said it was impossible to know how much oil had leaked off the Rena, "but it was only a small amount".

"While some of this oil appears to have reached the shoreline, it is unlikely to have a significant impact. The oil spill response team will closely monitor the situation over the weekend and remains ready to mount whatever response is necessary."

The amount of oil remaining on board the Rena is expected to be in the "tens of tonnes", which is still gradually being removed from the ship.

Maritime NZ said there were 649 containers now accounted for onshore, made up of 575 containers removed from the Rena, and 74 retrieved from the sea and shoreline.

It is though only two containers were dislodged into the sea on Wednesday night, but so far only one has been found.

Clean-up crews had also pulled large piles of wood and bags containing milk powder out of the water.

Maritime NZ said there was a two metre swell around the Rena at the moment, and conditions were expected to ease today and remain calm over the weekend.

Rough conditions had hampered the efforts of assessors to get back on board the Rena and assess the full extent of the damage and contents lost.