"From an environmental point of view we are very concerned should there be any leakage into the Ross Sea"
NZ conservation minister
It added that anti-whaling protesters, who had clashed with the Japanese fleet earlier this week, were not involved in the blaze as they were more than two days sailing away.
It is unclear whether the ship, currently disabled, will be able to restart its engines.
If it remains without power, New Zealand’s conservation minister said there were fears that it could threaten the fragile Antarctic environment if calm weather in the Southern Ocean, known for massive storm seas, turns bad.
"We don't need to stress that this is an extremely pristine environment with high biodiversity values," Chris Carter told a news conference in Wellington, New Zealand.
"We think there is up to 1,000 tonnes of heavy fuel oil on board the vessel, as well as many other chemicals. From an environmental point of view we are very concerned should there be any leakage into the Ross Sea."
Carter said if an oil leak occurred an international response would be launched involving New Zealand, Australia and the United States, which all have Antarctic bases.
The incident comes as Japan plays host to a specially-called meeting of the International Whaling Commission in Tokyo, to push it cause for a return to commercial whaling.
|Japan is hoping to push for a resumption |
of commercial whaling [Reuters]
The Nisshin Maru
is the 8,000 tonne flagship of the Japan whaling fleet in the Southern Ocean.
The fire is thought to have broken out below decks in the part of the ship that deals with the processing and freezing of whale meat.
The Nisshin Maru is one of at least two ships in the Japanese whaling fleet that has been targeted in recent days by anti-whaling activists from the Sea Shepherd group.
Protesters have thrown foul-smelling acid and other objects onto the Japanese whaling vessels to try to stop them hunting whales.
On Monday two Sea Shepherd ships collided with the Kaiko Maru whaler during a protest.
The Sea Shepherd vessels involved in that collision left the area on Wednesday after running low on fuel.
Neither boat was involved in the fire on the Nisshin Maru.
Commenting on the blaze Carter said he wished the ship’s crew "every good fortune" in fighting the fire. "Their efforts will be crucial to averting further catastrophe," he said.