Pirates latest blow to hit Rena salvage

There have been ravaging storms, rotting cargo and equipment overboard - now marauding pirates are being blamed for hampering the salvage of the Rena.

It has been revealed pirates plundered $20,000 of equipment without being detected that had been on board the barge RNG280 as it set sail from Singapore to Tauranga.

"They came up to the back side of the barge ... they must have been like monkeys," said Frank Leckey of Resolve Salvage and Fire, the company tasked with carving up the wrecked ship's bow on the Astrolabe Reef.

Mr Leckey suspected the pirates had watched as specialised salvage equipment was being loaded onto the barge in Singapore about six weeks ago.

"We are still trying to figure that out. I was in the shipyard and we had packed them into containers so people must have seen us doing this."

The pirates are thought to have climbed on board the barge at night and broken into the containers as it sailed through the Strait of Malacca.

"At night-time in the straits, there are so many fishing boats and it's hard for the captain to see who's coming close to us," Mr Leckey said.

"They all jumped on. There must have been a bunch of them because it took us a while to load ... and they off-loaded everything by hand and were gone."

Among the booty were boxes of magnesium welding rods used for cutting steel, fuel pumps, and other equipment.

"I don't know what they are going to use it for, there are very [few] people who use it in the world," said Mr Leckey.

"What seemed pretty silly to us was that there was 3000 gallons of brand new paint sitting right beside the rods ... normally, if they were going to steal something, they would steal paint."

The theft meant the company lost $20,000 it would not be claiming insurance for - and left it to pay another $20,000 for new gear, plus $15,000 extra for it to be flown in from the United States.

Incidentally, the raid came at the same time the company lost expensive gas-cutting gear that fell into the sea along with a chunk of the Rena.

"It was an unlucky day all round."

But Mr Leckey said the misfortune was not a big setback to the salvage - rather just a financial one.

The barge is now docked in the Port of Tauranga being prepared as a dive station for the next phase - going underwater to cut the bow down a metre below the tideline. That phase of the salvage is expected to finish on schedule before the end of the year.