Shaped explosive charges may be used to shift some of the containers aboard Rena, the container ship grounded on Astrolabe Reef since October 5.

With most of the oil now removed from Rena's onboard tanks, salvors are planning the next stage of the salvage operation – the removal of the remainder of Rena's cargo.

Tuesday morning's rising sun catches the port side of Rena. Photo: MNZ

On Tuesday, trials were undertaken with the 6000 tonne barge Sea Tow 60, to see if it can be anchored and manoeuvred using lines as it will be when it is used to take containers off the stacks on Rena.

Most of the containers will be able to be taken off using two cranes onboard the barge, says Svitzer salvage manager Captain Drew Shannon.

They have examined the twist locks securing the containers and he believes most will be able to be freed by men working from a cage suspended from one of the cranes onboard the barge.

The other crane, with a 280 tonne lift, will be used to remove containers as they are freed from their stacks.

Shaped charges are an option to cut the twist locks if they can't be freed using other means.

Meanwhile, air pockets continue to dog efforts to remove the remaining heavy fuel oil from the starboard wing tank – the pumps are drawing air, says Drew.

'It is being constantly monitored and once we get the air out, we will continue pumping,” says Drew.

On Tuesday, just over 22 tonnes of lubrication oil was removed from Rena's engine room and stored in deck tanks on the tug Go Canopus.

Maritime New Zealand has ordered 200 more ‘pingers' to attach to the containers on deck so they may be tracked should any more go over board.

On October 11, 88 containers were washed into the sea in rough weather, with as of last week, 58 remaining unaccounted for.

The figures can no longer be found on the MNZ website.

The beach clean-up is continuing with daily patrols still finding residual oil left after the oil washed ashore last month. Oil on the rocks round Mount Maunganui are now being washed off.

The process has been considered for Motiti, but there are difficulties, says national on scene commander Rob Service.

'The coastline is a lot more rugged.”

Two oiled penguins were brought to the mainland from Motiti on Monday, and another was found on the mainland on Monday night and taken to the oiled wildlife response village at Te Maunga.