|Officials say poor visibility is making it difficult to assess further damage caused to the ship [Maritime New Zealand]
A cargo ship that ran aground on New Zealand's reef last month is close to breaking up and and could spill more oil, worsening the environment disaster, maritime officials have said.
The Liberian-flagged Rena, which ran aground off the North Island resort area of Tauranga on October 5, is being battered by a storm, adding further stress to its already seriously damaged hull.
"The situation is looking increasingly precarious and we are preparing for the worst," said Maritime New Zealand's salvage unit manager, Bruce Anderson, as the weather deteriorated on Tuesday.
He said visibility and sea conditions were poor, making it difficult to assess what further damage had been caused and how many more of the ship's containers had gone overboard.
Anderson's warning came after officials had earlier said that the ship was still intact.
Officials said it was unsafe for anyone to remain on board but salvors had installed monitoring sensors on the vessel to measure how much the ship was moving and if it was tearing apart.
When the Rena ran aground, about 350 tonnes of oil spilled into the sea and was washed on to once-pristine beaches, killing at least 1,300 birds.
More than 1,000 tonnes of oil have since been pumped off the ship but another 300 tonnes remain on board.
Nearly 90 containers were washed overboard, 50 of which were unaccounted for, and 1,300 containers were still on board.
The owners of the ship apologised last month for New Zealand's worst pollution crisis, saying they were "deeply sorry" for the disaster.
They said it would not be appropriate to speculate on how the accident happened but described the ship's captain as "an experienced master" who had "an exemplary record".
A New Zealand court has since charged the Filipino captain and second officer with the discharge of harmful substances, which carries a maximum penalty of a fine of NZ$300,000 ($240,000) or two years in jail.
The pair were also charged with operating a vessel in a manner causing unnecessary danger or risk.
New Zealand's environment minister Nick Smith has claimed the Rena ploughed into the Astrolabe Reef while taking a short cut to reach port.
Maritime New Zealand said on Tuesday a barge attached to the ship's stern would drag the vessel to shallower water if it broke apart.
It quoted National On Scene Commander Mick Courtnell as saying the oil spill response team remained ready to respond to any oil that came ashore.
Mr Courtnell said hundreds of people were available for a large-scale clean-up effort should that be required.
"We had shoreline clean-up assessment teams out at first light, assessing the beaches where oil could come ashore. They have reported very small amounts of fresh oil along the beach between Omanu and Papamoa.
"We have New Zealand Defence Force personnel and volunteers ready to respond if a significant leak occurs."