Port of Tauranga planners and Maritime New Zealand staff are trying to track the containers that have washed off the container ship Rena aground on the Astrolabe Reef.

'They are doing their best to work out from the load plan which boxes have gone, and they are doing their best to track every one,” says Port of Tauranga chief executive Mark Cairns.

A container washing ashore at Motiti Island.

They are looking at photographs taken today to learn how many are missing.

An earlier estimate of 70 containers missing has been lowered to about 40, but the number is unconfirmed, says Mark.

Side scan sonar will be used to ensure all shipping channels within the harbour limits remain clear, and the port company will be working closely with MNZ and the harbourmaster to ensure that out to the coastal limit at the 12 mile mark also remains clear, says Mark.

'Once the weather settles the locations will be determined,” says Mark. 'If they are on the bottom the sonar canning will determine where they are and obviously the navigational hazards will be the ones floating semi-submerged.”

MNZ has issued a coastal navigational warning for all vessels to avoid moving between the Astrolabe Reef and Motiti Island, where the containers are currently believed to be.

'Obviously that's very dynamic,” says Mark.

'We provide updates to our customers and advise them to listen to the most up to date navigational broadcasts on Maritime Radio or the Sea Safety Net system, via the Pacific Ocean area satellite.

'The harbourmaster has issued a more specific advice that vessels approaching or leaving the port from the east approach or depart the port from a way point out closer to Mayor Island.”