After more than three weeks of active firefighting, the bushfire that ravaged Kangaroo Island has been declared contained.

Hundreds of firefighters worked tirelessly to battle the deadly blaze that has ripped through more than a third of the island.

In the video above: Tiny baby possum rescued by Kangaroo Island farmer

The CFS announced on Tuesday that the fire has been contained, meaning the forward rate of spread has been halted and no flare-ups have occurred outside the fire edge for a number of days.

"Crews have worked tirelessly to ensure that the fire edge has been blacked out and secured," the CFS said.

Flare-ups have caused concern for firefighters on Kangaroo Island. Credit: 7NEWS

Firefighters will remain active over the coming days to ensure the fire does not break containment as gusty, windier weather approaches.

Aircraft will be continuing to operate on the island in days to come should an outbreak occur.

#BookThemOut

The announcement comes a day after the state's tourism commission launched a new campaign in a bid to encourage travellers to visit.

The campaign, “Help them out, #BookThemOut” encourages tourists to make their way to bushfire affected areas to boost bookings and revive the local economies.

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In a statement, SATC Chief Executive Rodney Harrex said "Tourism across the country has taken a hit by recent events, and this campaign is an important immediate step forward in the sector’s long-term recovery.

“Help them out, #BookThemOut is a strong message that the Adelaide Hills and Kangaroo Island remain amazing, unique holiday destinations with incredible consumer experiences, and these regions need tourism to thrive and survive," he said.