Australia's Fraser Island is a world heritage site just off the northeast coast and the planet's largest sand island.
For six weeks massive fires have ravaged its low brush and rainforest amid the region's first major heat wave of the year.
The devastating bushfire began at a campsite on a remote part of the island, state emergency officials told local media.
State fire officials say that since Saturday, more than one million liters of water and fire-taming gel have been dropped.
So far, it has razed nearly half the island, also known by its indigenous name, K'gari.
In a statement issued on Wednesday, the state's emergency services warned tourists that they may need to evacuate, adding: "Conditions remain unpredictable and can change rapidly."
According to local media reports, several guests have been ferried away from the island as conditions worsened.
Total fire bans have been enforced in several parts of the northeast amid bushfire season which runs from late spring through summer.
Last summer's season, called 'black summer' by Australia's prime minister, razed more than 37 million acres of bushland, killed 33 people and billions of native animals.