After affecting 18 percent of the small 58 square kilometre (22 square mile) Amsterdam Island on January 29, the fire is now hitting 45 percent of its territory, the prefecture for France's French Southern and Antarctic Lands (TAAF) told AFP.

"There has been dry weather, and strong, shifting winds, with many changes of direction since January 15," said the prefecture, explaining the expansion of the fire.

"The fire is being allowed to burn, because given the isolation of the island, there is no way to extinguish the fire at the moment," it added.

Located in the middle of the Indian Ocean, approximately 2,800 (1,740 miles) kilometres southeast of the French overseas territory of La Reunion, Amsterdam Island is one of the most isolated islands in the world.

The 31 people -- mainly military personnel and scientists -- who were on the island when the fire broke out were all evacuated by boat the following day to Reunion.

It is not yet known what caused the fire.

Amsterdam Island is home to the Martin-de-Vivies scientific station, an internationally important site for monitoring greenhouse gas concentration worldwide.

"The base has been affected, the buildings are still standing but some water supply and telecommunications infrastructure is no longer operational," the prefecture said.

A French naval surveillance frigate Floreal was being despatched to the island to examine the current situation with firefighters and other experts on board.

They will go to the site to measure the progress of the fire, the extent of the damage and to investigate the causes of the fire, the prefecture said.

A haven for wildlife, the French Southern and Antarctic Lands, none of which have any permanent settled population, also include the remote Kerguelen Islands in the Southern Ocean.