Bay of Plenty Regional Council has drawn  a cautionary area around the grounded container ship Rena, following the release of a significant number of  containers and debris from the vessel overnight.

This includes the area from Waihi Beach to Mayor Island to Maketu. All vessels in the area are recommended to navigate with extreme caution.

All vessels should proceed at slow speed, keep a good lookout and travel through the area in daylight only. The debris field is extensive and its movement is unpredictable and could extend further.

The current Rena exclusion zone remains in place at this time - a three nautical mile radius around Astrolabe Reef.  This will be reviewed as more information is gathered about the state of the Rena.

Anyone found in the exclusion zone without the express permission of the harbourmaster may be or fined $200 or could be prosecuted.

Communities along the Bay of Plenty coastline are being advised that container debris and oil from the wreck of the MV Rena is likely to begin coming ashore tonight but  Maritime New Zealand (MNZ) says it has a coordinated response ready to deal with whatever washes up.

MNZ salvage unit manager David Billington says while both sections of the Rena are still on the Astrolabe Reef, the stern section had moved an estimated 30m from the bow section in seas of over 7m overnight, after the stern pivoted about 13 degrees to starboard.

“While the two sections remain on the reef, both are now open to the sea and vulnerable to more damage. The stern section is also listing heavily at about 24 degrees and is heaving in current swells of about 4.5m. The bow section is still firmly wedged in place on the reef, but it is open to flooding from the sea and is expected to deteriorate further in the rough conditions.”

MNZ salvage advisor Jon Walker said there was a strong likelihood that the stern section would capsize and sink, which would make recovering any further containers from that section considerably more difficult.

Container recovery company Braemar Howells estimate that between 200 and 300 containers of the approximately 830 remaining on the Rena were lost overboard when the two sections of the ship separated. Around 30 have been identified, with 17 tagged with buoys. However due to poor visibility and the rough conditions around the Rena, it is difficult to gain a more accurate count.

Acting operations manager Claudene Sharp said between 40 and 60 of the lost containers would likely be floating while the rest will have sunk. Those which had already been located would be collected when the sea state improved. A vessel equipped with sonar was searching for other containers, and the priority was to ensure that the shipping lanes remained clear. Several different vessels, including tugs, barges and landing craft, were also available to recover the containers and debris as soon as conditions allowed.

Ms Sharp said current weather patterns were pushing containers in a westerly direction between Astrolabe Reef and Mayor Island, and warned that debris or damaged containers could come ashore along the Bay of Plenty coastline over the next 12-24 hours.

Meanwhile, navigational warnings have been issued to shipping, with the port company communicating with individual ships via port radio and warnings issued to recreational vessels via Coastguard radio. Shipping lanes were also being monitored for containers and debris and the 3 nautical mile exclusion zone around the Rena remains in place, along with a 1500 feet no-fly zone.

The current bad weather is forecast to slowly ease over next 3-4 days, though seas are expected to remain rough with 4-4.5m swells.