"Given the fact storms occur from time to time, there's every likelihood more containers will end up in the sea."
The Pencaldo, a ship with a crane, had come from Australia to remove containers.
The cost of the oil spill clean-up was approaching $10 million - and Mr Key said in Tauranga yesterday the final bill could be 10 times more.
"I think if you're the salvor and you end up getting all the oil off and everything ... you don't get much change from $50 million, so add to that the ship, the clean-up costs, it's a big number, $70 million, $80 million, $100 million maybe."
The Crown had formed a Wellington-based legal team including experts in commercial and maritime law that was negotiating liability with the Swedish Club, insurer for the ship's owners, Costamare Shipping.
The insurers had stated their clients' cover included pollution liabilities and their obligations would be "met in full", Mr Joyce said.
But there were "boundary issues" lawyers were working through.
Port of Tauranga chief executive Mark Cairns said the crisis had not soured the company's relationship with Costamare Shipping or the Rena's lessees, the Mediterranean Shipping Company.
Analysts were gauging the disaster's effect on company stocks but the advice was that the effect was "not significant", Mr Cairns told the Herald.
The company was prepared for a long salvage operation and another large dump of containers would not pose major navigation risks.
Last night, Mr Cairns said closing the port for a day cost about $500,000, but the only disruption had been a brief overnight suspension which delayed two vessels six hours.
He earlier told shareholders at the company's annual general meeting there were "initial hopes" the Rena could be refloated after it hit Astrolabe Reef on October 5.
"That simply didn't prove feasible, given how far up on the reef the vessel ended up," he said.
A shareholder who asked if a beacon would be put on the reef was told it would depend on the result of several investigations.
On board the Rena, efforts to pump out the 228 tonnes of oil in the port-side tanks into the tugboat Go Canopus had been slow because of extensive damage to the ship's hull.
Divers were also toiling in murky conditions to build a dry "coffer dam" through a corridor in the ship so the submerged starboard-side number 5 tank, holding 358 tonnes of oil, could be accessed.
About 6700 volunteers had registered for clean-up work on affected beaches, with more encouraged to turn up at Mt Maunganui's Tay St and Taylor's Reserve in Papamoa today.
Equipment, including mechanical "sand-sifters", was being trialled. Oil was still appearing along the foreshore at Papamoa, and a base had been set up at Whangamata as Maritime NZ monitored a five to 10-tonne slick that leaked from the Rena on Saturday.
COUNTING THE COST
$10 million - estimated cost of the oil spill response so far
$100 million - possible cost of the entire disaster
1288 - containers still on board
1335 - dead oiled birds found
