Fire crews worked for 12 hours to tackle two stack fires which were started by arsonists and destroyed thousands of tonnes of straw.
Fire chiefs also warned that one of the fires, started in the early hours of today, could still be burning on Saturday.
Crews from Whittlesey, March, Chatteris and Yaxley were called to the first stack fire on a farm in Burnt House Road, Turves, in the early hours of today.
When they arrived just before 3am they found a large stack measuring about 60m by 50m alight and a lorry trailer of straw ablaze.
A fire service spokesman said: 'Crews set up two jets to prevent the fire spreading to nearby farm buildings.
'Two light portable pumps pumping water from open water sources were set up, along with two covering jets and two ground monitors and a water curtain, to contain and extinguish the fire.'
It is believed about 2,000 tonnes of straw was involved in the fire. Firefighters worked with farmers using teleporters to remove bales of straw which were not burnt.
At 2.45pm, the blaze was brought under control and the final fire crew at the scene left a short time later.
The spokesman said: 'The stack is expected to burn for up to 72 hours. Regular re-inspections will be made by the fire service.'
At 6.45am, while crews were tackling the blaze in Turves, fire control received reports of a second stack fire in Benwick Road, Whittlesey.
About 20 bales of straw were well alight in the open, located about three miles from Benwick.
The majority of the fire was extinguished by 9.20am, with firefighters from Yaxley working with a farmer to drag the straw and extinguish the remaining flames.
• Anyone with information should contact police on 101 or Crimestoppers anonymously on 0800 555 111.
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