More than 150 firefighters are back at Wareham Forest.
They're trying to keep on top of flare-ups but strong winds are making conditions difficult.
For the second time this week a major incident has been declared in relation to the ongoing fire at the forest.
The fire service has requested a helicopter from Wales to assist.
An area of heath and woodland equivalent to the size of 115 football pitches has already been destroyed by a major fire which broke out at the forest on Monday.
It was declared a major incident later that night, with 150 firefighters at the scene at the height of the disaster.
Efforts were scaled back on Tuesday and a number of firefighters have remained at the forest since.
Now, crews from across the county have been called back to deal with flare-ups.
A spokesman for the fire service said: "With resources stretched you can do your bit by being extra careful in and out of the home.
• No bonfires.
• Do not leave cooking unattended.
• Make sure any personal smoking items are fully extinguished.
• Remain vigilant
The smoke has travelled as far as Bournemouth, Poole, Ferndown and Wimborne.
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