Maritime New Zealand says oil pollution remains the main priority in dealing with the container ship grounded off the Tauranga coast.
The Rena, owned by Greek company Costamare Shipping, was heading towards Tauranga from Napier when it ran aground on 5 October carrying 1700 tonnes of fuel and more than 1300 containers, including 11 with dangerous goods.[image:3337:half:right]
As much as 350 tonnes of the oil has now leaked, but three salvage experts who spent five hours aboard the vessel on Thursday are confident that the biggest tank containing 770 tonnes of oil has not ruptured.
Maritime New Zealand says tests carried out on Thursday show that the oil dispersant Corexit 9500 is not working and other options will have to be considered.
A testing crew got up in a helicopter on Thursday for the first time since two inconclusive tests of the spray last week.
They sprayed 200 litres on fresh oil about 600 metres from the listing ship but the national dispersants adviser to Maritime New Zealand, Leigh Stevens, says it is not effective enough to justify further aerial spraying.
Eighty-eight containers have fallen off the Rena, including one containing the dangerous chemical alkyl suphonic acid - not the potentially explosive ferro silicon, as Maritime New Zealand earlier reported. Its whereabouts is not known.
Salvage manager Bruce Anderson says 48 of the containers are empty and others contain milk powder and other dairy products, timber and animal pelts. About 20 containers washed ashore on Thursday.
Mr Anderson says a specialist company has been engaged to find containers in the water using sonar equipment and has the technical expertise to remove them from beaches.
About 500 people have been clearing up beaches around the Bay of Plenty on Thursday, removing more oil and debris. Some 100 tonnes of waste has now been collected from shores.
Six vessels collected debris on the water and Maritime New Zealand says another two would be readied to collect oil using special booms.
Port of Tauranga says it will close from 9pm on Thursday until 6am on Friday to allow a search of the main shipping channels for debris and floating containers from the Rena.[image:3335:full]
Ship appears 'more stable'[image:3336:half:right]
Maritime New Zealand says a big crack in the ship's hull does not appear to have worsened and the vessel has turned about 30 degrees into deeper waters on Thursday, making it more stable on the reef.
The authority had been concerned that the stern might break away, and tugs have been on the scene trying to hold that part of the vessel steady.
Transport Minister Steven Joyce says the salvage team that went on board the Rena on Thursday morning will report back to the salvage company's control centre before any further decisions are made on what action to take.
Maritime New Zealand says the fact that the containers on the deck are moving makes it extremely dangerous for salvage crews to work on board.