Divers assessing the partially submerged fuel tank on board the Rena got the shock of their lives when they found a power system inside the ship was still operating, three weeks after the container ship hit the Astrolabe Reef.
Maritime New Zealand salvage unit manager Bruce Anderson said divers were assessing the 5 starboard tank yesterday when they found power still operating inside the damaged hull.
"They suddenly found the switch and turned it off," he said.
"Fortunately no one was injured in that."
Volunteers will be cleaning up a fresh oiling around Mount Maunganui and Leisure Island and between Tay Street and Maketu Spit today.
"This looks like oil that was buried under the sand during the rough weather that occurred a couple of weeks ago," National On Scene Commander Nick Quinn said.
"The movement of tides and sand has brought it again to the surface, and so we now have a new layer of oil to remove."
Mr Quinn said the oil had settled in a band along the high tide line and up towards the dunes.
During the past three days about 848 tonnes of waste was collected off beaches.
The coastline from Papamoa to Maketu would remain closed for the near future, as experts conducted regular water samples.
Meanwhile, pumping had temporarily stopped from the port number 5 tank yesterday as salvors moved the pump deeper into the tank.
"Most of the oil has been removed from that tank, so the fuel transfer rate out of there is slowing down," Mr Anderson said.
The salvage team had begun pumping fuel from the engine room tanks into the port number 5 tank but this had proved ineffective, Mr Anderson said.
Salvors were now working on a pumping system to take the fuel through a 10cm hose and directly into the anchor-handling tug Go Canopus.
The bollard tug replaced the Awanuia and established a connection with Rena last night.
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About 737 tonnes of oil has been removed off the vessel - 373 tonnes from the port number 5 tank, which initially held 772 tonnes.
Mr Anderson said the Go Canopus was capable of maintaining a close position to the ship in poor weather conditions, however, the weather forecast for the next five days was relatively clear and pumping was due to continue throughout this time.
Pumping to the Go Canopus was likely to be a slower method than using ship pumping equipment and existing pumping methods, however, it was the best option available, Mr Anderson said.
Salvors continued to focus on removing oil from the 5 starboard tank before shifting their interests to the three settling tanks, which hold 112, 116 and 25 tonnes respectively.
"This is really challenging as the tank is under water and the team needs to create a water-tight space to work from," Mr Anderson said.
As far as container recovery went, Mr Anderson said it was highly likely containers would be recovered in pieces, not one, intact container.
There was 1673 tonnes of oil on board the ship when it grounded and initially spilled 350 tonnes of oil overboard. A further 5-10 tonnes of oil was lost on Saturday night.
Maritime New Zealand said contingency planning was under way for the possibility of the remaining oil from the weekend's oil spill, which is due to come ashore on Tuhua (Mayor Island) and the Coromandel Peninsula in the next few days. A wildlife stabilisation centre has been established on Mayor Island and booms are being organised to deploy there if needed.