Updated: 1.16pm -
Port of Tauranga chief executive Mark Cairns said the port had not yet heard from the Harbourmaster on the recommended shipping route to the port since the sinking of the stern.
Normal shipping movements were continuing, he said.
"Ships arriving and departing the port should exercise extreme caution and maintain a vigilant lookout."
The salvors had "significant marine resources" on station to attend to any further lost containers, Mr Cairns said.
"Current predictive modelling is suggesting any lost containers will drift in a southeasterly direction, away from the Astrolabe Reef.
Updated: 1.04pm -
The stern section of the MV Rena is perched on the edge of the Astrolabe Reef, with about 75 percent submerged and the remainder sticking up out of the water, Maritime New Zealand says.
A small amount of oil has been released from the stern section, along with debris - mostly timber - and a small number of containers.
The first oil is expected to reach Motiti Island this evening, with more predicted to reach the shore at Pukehina tomorrow, National On Scene Commander Alex van Wijngaarden said.
"This was not unexpected," Mr van Wijngaarden said.
"We are prepared, and we will deal with it."
Oil spill response teams are gearing up to clean up the oil, including placing booms in sensitive areas, and the oiled wildlife centre in Tauranga is being reactivated. The volunteer programme is also being reactivated.
The amount of oil released has not yet been calculated, but is known to be only a fraction of the size of spill released last October.
Container recovery company Braemar Howells estimates that 400 containers are in the stern section of the Rena.
Spokesman Grant Dyson said that two tugs have been sent to the Rena to try and contain drifting containers, and also tow any floating containers to a specialised recovery barge that was being deployed.
The tug Go Canopus is still connected to the stern section of the Rena. This morning when it became apparent that the angle of its list was changing, salvors took the opportunity to try and use the tug to reposition the rear section on the reef, which would have enabled the container recovery barge Smit Borneo to move in closer. This proved impossible.
The bow section of the Rena remains in its original position on the reef.
Meanwhile, work is continuing on-shore to deal with the debris released at the weekend when the two sections of the Rena separated on Saturday night.
Fifty people are working on Waihi Beach today, made up of iwi, Allied Workforce and staff from mining company Newmont. Another 30 people are working from Papamoa to Kaituna Cut and a further 20 are on Matakana Island.
Debris retrieved from the water yesterday has already been brought ashore at the Port of Tauranga. Work is also planned to empty the containers which landed on Waihi Beach yesterday, so the empty containers can be removed.
More than 20 containers beached on Matakana Island overnight and planning is underway to deal with these, Mr Dyson said.
Braemar Howells has activated 11 hubs, which are mini coordination centres, along 100km of the coast. An agreement between the company and iwi provides for their local labour force to be associated with debris clean-up efforts.
Anyone wishing to assist with cleaning beaches should register on-line through the Bay of Plenty Regional Council's website www.boprc.govt.nz/oilspillvolunteers
Updated: 12.14 -
Svitzer spokesman Matt Watson was watching from the air when the stern section fell off the reef.
It took about 40 minutes for the aft-end to slip slowly backwards.
"The stern, the rear-section, has tilted further over to the starboard side and it has slid back. About 75 per cent of the rear-section is now submerged.
"It appears to be perched on the reef's edge," he said.
Svitzer salvors were in a helicopter over the wreck as it began to sink, and Mr Watson said it is possible the stern might have temporarily re-settled into its new position.
The barge Go Canopus was attached to the hull when it began to sink.
"The Go Canopus was attached at the time. It played a role. It powered up when it was clear there was a lot of movement," he said.
It is unclear yet what role the crane barge played and whether it was responsible for the rear-section sinking, he said.
Updated: 10.42 -
Most of the stern section of the MV Rena has slipped off the Astrolabe Reef.
As at 10.38am, the foremost part of the stern was still sticking up out of the water, with the rest - including the bridge - submerged.
The bow section remains unchanged in place on the reef.
Personnel from Maritime New Zealand and Svitzer Salvage have been airborne to monitor the slow progression of the stern into the sea since the vessel's status began to change rapidly after 8.30am today.
"The accommodation section, the white part that sticks up, is beneath the water. The front of the aft part of the ship is still above water and it's still upright at this stage," a Maritime New Zealand spokeswoman told the Bay of Plenty Times.
The aft section is larger of the stricken cargo ship, which ran aground on the Astrolabe reef off Tauranga in October.
There was no one on board.
Information about any further release of oil, debris or containers from the Rena will be released as soon as it is available.