High sea swells overnight have caused further damage to the hull of Rena as salvors prepare for the worst, with more rough weather expected in the region.
MetService has issued a strong wind advisory for the Bay of Plenty, with gales and large swells expected to peak tonight.
Winds are expected to peak at 35 knots tonight with the sea becoming rough, and rain this afternoon in the Bay of Plenty reducing visibility and raising the risk of more oil spilling and containers falling overboard.
Salvage efforts were suspended yesterday due to bad weather, which caused the hull on the starboard side to buckle further last night, said Maritime New Zealand Salvage Unit Manager Bruce Anderson.
The ship is still holding in one piece at the moment; however, it was looking "increasingly precarious'' and salvors were preparing for the worst, he said.
The team is on board the tug Go Canopus, which is connected to Rena, and are keeping a close eye on the stricken vessel.
An observation flight this morning had to turn back at Motiti Island because of the poor weather.
Mr Anderson said Go Canopus would try to tow the stern to shallower water if it detached from the bow, but the tug would only remain connected as long as it was safe to do so.
"Rena held up well through the bad weather two weeks ago, but we may not be so fortunate this time,'' Mr Anderson said.
Specialist container recovery company Braemar Howells Ltd has been contracted to deal with containers that may be released from Rena, and has four tugs on standby in Tauranga, with another two on site monitoring Rena in case containers fall overboard.''
The suspension of salvage operations meant there was no further progress made in sealing the coffer dam to give access to the final starboard number five tank.
No oil has yet been pumped from the tank, which contains 358 tonnes of heavy fuel oil and is submerged below the waterline.
Maritime New Zealand salvage unit head Kenny Crawford said achievements had been made during the recent period of fine weather. Four of the five main heavy fuel oil tanks have been emptied and more than 1000 tonnes of heavy fuel oil had now been recovered from the Rena.
There is an estimated 350 tonnes of oil remaining in the starboard tank, which is currently intact.
"It has been an extraordinary effort to get as far as we have and remove over 1,000 tonnes of heavy fuel oil from the ship, but we have always been at the mercy of the weather. The possibility of the ship breaking up has always been on the cards,'' said national on scene commander Mick Courtnell.
Volunteers have given just over 11,000 hours of their time to help.
Co-ordinator Pim de Monchy said volunteer numbers were up slightly over the weekend with 200 on Saturday and 160 on Sunday. So far there have been 3732 participants.
Except for the main beach from Mauao to Tay St, beaches remained closed.
- APNZ and the Bay of Plenty Times
