Arson attack on 66,000 tonnes of straw in Cambridgeshire
Arsonists are suspected of setting more than 66,000 tonnes of straw on fire in eight separate blazes in Cambridgeshire.
Up to 16,000 tonnes have been on fire in Mepal since Tuesday night.
A further 50,000 tonnes is now understood to be on fire in a field off the A142 at Witcham Toll near Ely, said Cambridgeshire Fire Service.
The smoke from the fires can be seen from almost 30 miles away. The stack is expected to burn for several days.
The fire service commander co-ordinating the operation said he believed the fires were "suspicious".
Police said they had sealed off the area at Witcham Toll which they were treating as a "scene of crime".
Cambridgeshire Fire Service is now considering sending more crews as the direction of the wind is changing.
Much of the straw was destined for the nearby Elean Power Station, close to Ely, which is the largest straw burning power station in the world.
There are several stacks on fire in the Mepal area - roughly 32,000 bales, or about 16,000 tonnes - and several on fire in the Witcham Toll area - roughly 100,000 bales, or about 50,000 tonnes.
The exact number of stacks on fire is difficult to tell as they are very close together.
Chris Parker, station manager for Cambridgeshire Fire and Rescue Service, said: "These are very large fires and as with all smoke, it does have a degree of toxicity.
"We would advise all residents and drivers affected to keep windows and doors closed and to contact NHS Direct if they experience any adverse affects.
"At the moment, the smoke is blowing across fields towards Witchford, but if the wind direction changes we will issue further advice."