Maritime New Zealand is clarifying the status of the container ship Rena by saying it is in one piece.

A MNZ spokesperson says the most up-to-date information is that Rena has significant cracking on both its port and starboard sides, but the vessel is in one piece.

Rena, photographed today resting on the Astrolabe Reef about 25km from Tauranga. This picture shows its port side has a considerable crack, from deck to waterline.

Svitzer is the appointed company undertaking the salvage and its salvage master, Captain Drew Shannon, said this afternoon: 'It is one ship.”

The ship is in a volatile condition though, described this morning by MNZ salvage unit manager Bruce Anderson as 'broken in two”.

'It's grinding and creaking – it is the sound of a vessel dying.”

Mr Anderson has worked without break as the manager for the salvage unit since Wednesday, October 5, when Rena ran aground on the Astrolabe Reef.

A shift rotation sees him replaced by Andrew Berry as salvage unit manager for the next two days as he takes a rest.

Captain Shannon agrees the ship is in a dangerous condition, including a 21 degree list, and the safety of his team is first and foremost in their activity.

'It is in a serious condition so we have to take this carefully.”

The team's priority work is the pumping of oil from the ship and onto a barge, Awanuia, stationed at Rena's stern.

Oil has pumped without interruption from the Rena and overnight 21 tonnes of the 1300 tonnes believed to be onboard was processed through to the Awanuia.

It may appear a slow process, but Captain Shannon says this is the only way as the entire pumping system is new with equipment customised for this operation.

'We start slowly, we prove the system and then once proven we look to improve the system.”

It is completely different from the pumping undertaken last week in which Rena's pumps were used in the process – these are not usable now owing to extensive onboard damage.

Stormier conditions are expected at sea tonight with this increasing risk for the salvage team.

For the current pumping process to continue, salvors need Rena to stay in one piece and to remain where it is perched on the reef.

A MNZ spokesperson says the ship remains perched on the reef in the same way as it has for the last week.

Following last week's storm, the ship moved about 30 degrees, placing it more firmly on the reef.

If the ship breaks and fuel tanks go down with its stern section, the salvage team prefers for it to be in shallow water as they can more easily handle their operation there than in deep water.

Mr Anderson says if the ship moves off the reef it could puncture a fuel tank causing more oil to leak.