Arsonists set fire to hundreds of bales of straw near Soham on Wednesday night.
Firefighters from Ely was called to a stack fire near the BP garage on the A1123 at the junction with the A142, shortly after 7.30pm.
About 340 bales of straw, measuring 40sq metres, were on fire and an additional crew from Ely was requested to support fire-fighting efforts.
Crews used hose reels and beaters to contain the fire to the stack and prevent it spreading to adjoining stubble fields. Crews had extinguished the majority of the fire by 12.33am.
A relief crew from Littleport remained on site until about 3am to monitor the stack and ensure embers did not spread the fire to a nearby hedge line.
The straw did reignite again and at 4.39am a crew from Soham attended to monitor it. The crew returned to their stations at 7.30am.
The cause of the fire is believed to be deliberate. Anyone with information should contact the police on 101 or the independent charity Crimestoppers anonymously on 0800 555111.
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