Cheese, pies and milk sachets are among the debris to have fallen into the sea around Rena during the salvage of the containers on its decks.

This pollution is an environmental hazard and creating difficult working conditions for salvors.

Photos supplied to SunLive show the extent of the difficult conditions experienced during container removal from the ship grounded on Astrolabe Reef since October 5.

Salvors try to access one of the crushed containers at the stern of Rena.

During the lifting of crushed containers, cargo contents have fallen out, into the water and onto the decks of the Rena, and surrounding vessels.

Matthew Watson, the spokesperson for Svitzer, the company in charge of the container removal operation, says container contents are an environmental hazard, but the risk of lifting the containers off outweighs the risk of leaving them onboard.

'The main concern is the environmental impacts.

'You would rather lift a container off the vessel and from time to time loose five per cent of the contents, rather than have the whole container go over and spill out onto the ocean.”

Matthew says the instance of contents falling out is 'very rare” but has happened on occasion in the last two weeks.

He says crushed containers are very difficult to access and it is not until salvors get close enough to lift containers they know how they are going to deal with each one.

Contents including cheese and pies in the water next to Rena.

'They need to make the most educated decision they can, whether they can lift and swing the container from position A to position B.

'If stuff spills out, it is not ideal, but not unexpected and they will move in to clean it up.”

Salvors are constantly monitoring the salvage operation and tug boats are on standby around the vessel to move in and scoop up any contents that fall into the ocean.

Matthew says tugs are well equipped with the materials they need to lean over the sides and scoop any rubbish or contents.

These tugs are also there to respond in case the vessel breaks or more containers fall overboard.

Refrigerated containers are proving particularly dangerous for salvors as meat and other foodstuffs decompose causing a stench onboard the vessel.

'There are gases onboard, the products in containers naturally gives off gasses.”

Debris spills from this cracked container as it is lifted from the Rena.

Maritime New Zealand salvage unit manager Kenny Crawford says health and safety conditions onboard the Rena are being constantly monitored, including gas detection.

Industrial chemists are working onboard the Rena to monitor the working environment and Matthew says if at any time it becomes hazardous the ship will be evacuated.

There were 1368 containers onboard the Rena when it ran aground on Astrolabe Reef on October 5.

Eighty-eight of those containers fell overboard during a storm on October 12.

Salvors have been able to lift 166 containers from the Rena, stopping intermittently due to rough seas and strong winds.

Containers at the stern of the ship are the first to be removed.