Crews from Manea and Chatteris took nearly two and half hours to deal with a stack fire.
The fire broke out in Byall Fen Drove, Manea last night (Thursday)
Cambs fire chiefs said it involving two stacks.
In total there were about seven tonnes of straw material affected.
One stack was well alight and the other was smouldering with smoking blowing across the road and drivers were told approach the scene with care.
Crews pumped water from a nearby open water source and used jets to put the fire out.
They returned to their stations by 8.10pm.
The cause of the fire is unknown.
Police issued warnings throughout the evening to be aware of smoke drifting across the highway.
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