Salvage crews scrambling to avert an environmental disaster in New Zealand's pristine Bay of Plenty battened down a stranded ship carrying 1,700 tonnes of oil on Monday as stormy weather loomed. Fearing that the container vessel Rena would break apart in heavy seas and sink on the reef it struck last Wednesday, salvage teams installed covers designed to seal the ship's fuel tanks if it ends up on the sea bed. They also lashed down shipping containers on the vessel's deck and moved the fuel from damaged tanks at the front of the vessel to more secure ones in the stern, Maritime New Zealand (MNZ) said. MNZ salvage unit manager Bruce Anderson said sensors had been installed on the Liberian-flagged ship to alert officials if stress from rough weather began to tear the hull apart. "That's a possibility, the weather is something we're keeping a close eye on along with the ship's structure," he told Radio New Zealand. "Obviously the potential for serious consequences is there, and we're under no illusions about that -- that's why we're trying to work around the clock to get the oil off." The government has warned that if the ship sinks and spews oil into the Bay of Plenty, which is home to whales, dolphins, penguins and seals, it could create New Zealand's largest maritime pollution disaster in decades. The official forecaster MetService issued a severe weather warning for the bay, predicting that heavy rain and winds gusting up to 90 km/h (56 mph) would hit late Monday. The salvage teams worked through the night, hoping to remove the oil before the bad weather arrived, but Anderson said that by Monday morning only 10 tonnes had been pumped onto a tanker moored beside the stricken vessel. MNZ said safety concerns meant that pumping had to be suspended. Discharge from the ship has already created a five-kilometre oil slick and killed a number of sea birds, with seven Little Blue penguins and two shags beng treated at wildlife rescue centres after being found covered in oil. Some 250 people, including specialists from Australia, Britain, Holland and Singapore, have joined the oil slick response team, with 300 defence personnel on standby in case they are needed for shoreline clean-up work.