Sand washing is the latest technique being used by Maritime New Zealand to clean up the after effects of the October oil spills from the container ship Rena.

Sand washing is where a bobcat takes a bucket load of oil contaminated sand to the surf to let the natural wave action sort the clean sand from the oiled sand.

A bobcat commences the sand washing process.

'It is the first time we have used this technique on this particular operation,” says MNZ national on scene commander Rob Service.

The clean up effort is also continuing trials with beach cleaning machinery.

Clean up operations continued at five different locations today with 320 people working. These people were NZ Defence Force personnel, contractors and volunteers.

Low pressure rock flushing round the northern side of the Mauao is continuing.

On Astrolabe Reef, salvors are continuing to have difficulties pumping the remaining heavy fuel oil from the starboard five wing tank.

They believe air trapped in pockets in the ship's steel framing is responsible.

'Over the last 24 hours work has been ongoing trying to purge the air from the tank,” says salvage unit manager Arthur Jobard.

The 20 men onboard are throwing all their resources into trying to find a solution.

MNZ salvage advisor Jon Walker says it is a trying and frustrating process; setting up the pumps, starting them, stopping them when the air gets in, and resetting, is a process that takes hours each time.

'They are absolutely furious that they can't get this oil off,” says Jon.

About 20 tonnes of salt water contaminated lubrication oil also remains onboard.

At the Te Maunga oiled wildlife centre there are 403 birds in care.

No new oiled sea birds have been found in the last 24 hours.

Two birds are in the process of being de-oiled.