Oil continues to swamp the region's shores and now rogue containers have added yet another hazard out at sea.
Cargo toppled off the deck of the listing Rena yesterday as the ship was hammered by off-shore gales and rough swells.
The containers now floating in the sea off the Tauranga coast pose a menace like icebergs for passing vessels.
Navigational warnings have been issued and major shipping has been re-routed. Some cargo has washed ashore at Motiti Island.
General secretary of the Maritime Union of New Zealand Joe Fleetwood said the containers would pose a serious threat for all seafaring vessels until every container was accounted for.
"It's a massive hazard. It's like an iceberg, 80 to 90 per cent is submerged under water.
"If a yacht or small pleasure craft struck one they would disintegrate. A big ship hitting it, it has the potential to hole it," he said.
Mr Fleetwood said the problem would extend well beyond the Bay of Plenty coast. "They have to put a warning out across all of Australasia. Just because they may sink, they will be carried in the current and pop up.
"Nothing will be safe until they can account for all ... the containers," he said.
Yesterday the count of fallen containers had reached 27 but Mr Anderson said as many as 40 may have toppled overboard.
There were 1368 containers on board. Eleven containers containing hazardous substances were still on the vessel.
Even if the ship remains above water, it is highly likely that more will come off due to the current severe weather conditions and the vessel's heavy list.
Maritime New Zealand salvage unit manager Bruce Anderson said the Rena was listing 15-20 degrees to starboard.
He said a large number of containers were floating near the vessel and because of their buoyancy it could be assumed that many were empty.
The floating containers, some of which remain tressed into stacks of three or more, were the responsibility of the salvors while those that washed up would be dealt with by the police.
Tugs belonging to salvage company Svitzer were yesterday attempting to round up the floating obstacles and pool them together.
"The container recovery plan is in action. They are corralling those containers.
"They have to lasso them, like cattle. It's exactly the same as that," Mr Anderson said.
A specialist cargo ship was expected to arrive today. The Polcoma is equipped with a heavy lifting crane and will be able to lift the containers from the water on to its deck.
Port of Tauranga chief executive Mike Cairns said the unfolding crisis was unbelievable but insisted the port remained open.
He said a warning had been issued for vessels approaching from the east to avoid the area between Motiti Island and instead travel near Mayor Island.
Defence Force and Maritime New Zealand crews were scanning for submerged containers in open waters yesterday and port vessels will begin monitoring the harbour limits closer to shore today.
Port tug boats will search for hidden containers by towing specialist sonar equipment and a magnetometer.
"Containers are a priority. If they're semi-submerged they're a significant problem," he said.
Catherine Taylor, director of Maritime New Zealand, said the wayward containers must be handled by the authorities.
"The on-water recovery of containers is the responsibility of the salvors. The on-shore responsibility is the police," she said.
Containers that wash on to beaches should not be opened by locals.
Mr Anderson said the contents could be unpleasant. Some of the containers contained skins and pelts, he said, which would have become "hot and smelly".