"The stern is in a precarious situation. It's not quite as stable as we once thought."
Divers have been inspecting the port and starboard side of the vessel over the last two days, he said.
"The message that they're sending back to us is that the vessel is sitting with a portion of it still in space, so it's not as stable as we had hoped."
He said if the weather turned, there was a chance 100 tonnes of oil in the duct keel could leak out.
Mr Anderson said a salvage expert deemed the ship one of the worst wreck he'd ever seen.
"This thing was grinding and groaning away as the vessel was twisting and mashing parts of it up. He was saying it's one of the scariest he's seen."
MNZ scene commander Nick Quinn said the oil extraction process would be in "difficult and potentially hazardous conditions," as the ship is still on a 21 degree list.
Four platforms had been attached to the side of the ship to hold welders, power packs, generators and machinery to complete the oil extraction.
An Archimedes screw pump will be inserted into the tank to extract the oil hardened to a consistency of "marmite", he said.
The salvors were to be helicoptered off the boat today and would try to return tomorrow, he said.
Containers
MNZ scene commander Nick Quinn said the search for missing containers widened today.
Approximately 44 of the 88 missing containers had been found, he said.
The team the team today searched a wider area to try and locate floating or sunken containers.
He said there was still a possibility of more containers falling off the boat, as it is still on a 21 degree listing.
MNZ salvage head Bruce Anderson said hazardous containers had been identified as being on the ship.
Rubberneckers
It's been a sunny day interspersed with showers in the Mount, and dozens of walkers, runners and observers are in the area for the start of the weekend.
Beach access remains restricted from Mt Maunganui to Maketu, and will remain in place until it is reassessed on Monday.
While clean-up efforts are underway at oil-stricken areas across coastal beaches, at the Mt Maunganui beaches it appears business as usual.
Dozens of rubberneckers have lined the coastal dunes with binoculars to try and glimpse the helicopters and vessels surrounding the stuck cargo ship, and a handful take their chances by heading on to the restricted beaches.
A few determined locals even braved the authorities to scoop remaining oil into plastic bags this morning, said one local.
Environment minister Nick Smith met with local iwi, tourism operators today.
"The situation has improved substantially, but we're not out of the woods yet."
He said the Government was working with the Chamber of Commerce on a potential support package.
Clean-up
An army of volunteers have joined the oil spill response team today to continue cleaning oil washed up on beaches, Maritime New Zealand scene commander Nick Quinn said.
More than 4200 people have registered to volunteer, and an estimated 2000 people were involved in efforts today.
Mr Quinn said it was important to keep the momentum that had been built up over the last days.
"We have made really good progress, we are beginning to achieve our objectives and we need to keep it up."
An estimated 376 tonnes of waste has been collected and potentially toxic waste is being sent to a waste-holding plant in Hamilton.
MNZ chief Catherine Taylor said the focus was now on keeping uncontaminated areas clean.
"The quicker we can get the beaches cleaned up, then we can get them open again.
"There is now noticeably less oil on the beaches, we will be testing the beaches to determine how far the oil has spread over the weekend as well."
Environment minister Nick Smith said 70 per cent of the beaches had been cleaned.
Tauranga City council has also closed the Sulphur Point and Pilot Bay boat ramps to contain the spread of the oil.
A preliminary assessment of the coastline from Opotiki to East Cape has been undertaken to plan for projected oil reaching beaches there.
A volunteer centre at Whakatane today trained workers ready to take action if oil arrives on their beach.
Volunteer training and equipment deployment in the eastern region is also taking place, as tidal projections show the oil could be headed towards the Eastern coast waters.
Wildlife
The bird death toll has nearly reached 1000.
The Wildlife centre now has a total of 130 oiled birds in their care, 55 of which are little blue penguins.
The penguins have been cleaned, but many need to be waterproofed before they can be released.
The centre has contained 25 of the 100 rare dotterels known to be in the Bay of Plenty area, and are building a special aviary to protect the birds.
Dr Brent Stephenson said the estimated 990 dead birds had been brought into the facility, and had been sorted and documented.
Four fur seals had been brought in, and three will be released over the next few days he said.
He said the facility had been expanded and could now care for 500 birds.
* An earlier report incorrectly stated that the oil aboard the Rena would need to be heated before it could be pumped off the vessel. It was also incorrectly stated that the boat ramps at Whareroa and Fergusson Park were closed. The errors were obtained from a press release issued by Maritime New Zealand, which has since advised of the corrections.
