Norfolk fire service said the pile of waste wood, which caught alight on January 21, had reduced in size by 70pc since that time.
But this afternoon it said it expected it to burn for a further four or five days before smouldering for a further fortnight.
The fire service, Environment Agency and council environmental health officers are continuing to visit the site at Manor Farm daily to monitor for air and ground water pollution.
Until the fire is extinguished, people near the site are advised to keep their doors and windows closed and avoid spending time unnecessarily outdoors.
Drivers who travel through the plume should keep windows closed and turn off air conditioning and air vents.
More than 40 firefighters were called to the scene of the blaze, which broke out in a stack of waste timber piled 15m high 16 days ago. As yet it is not clear what the operation will cost.
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