Several crews were dispatched to the woods, including support from the Derbyshire Fire and Rescue Service.
A spokesman said this afternoon (Wednesday): “At present, we have crews from Mansfield, Ashfield and Worksop on site tackling the fire, which has covered an area of 4,000 square metres.”
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Ashfield fire station reported on its Facebook page that the fire was “deep-seated”. It added: “But we will extinguish it and keep our communities safe.”
It is not yet known how the blaze started, but the hot, dry weather is putting farmland and woodland at risk, while grass fires are igniting across the county.
People are being urged not to start barbecues or camp fires on open grassland, nor even discard cigarettes.
Yesterday and overnight, up to 85 firefighters battled to bring under control a major fire at Blidworth, where residents had to be evacuated from their homes for a while.
Earlier this week, the Nottinghamshire and Derbyshire fire services revealed that their control room had taken 906 calls in a 36-hour period, against an average of 110 in 24 hours.
Emergency call handlers took an increase in calls of 312 per cent on Monday and Tuesday. At one point, 999 calls had to be diverted to the Tyne and Wear fire rescue service due to the high demand.
Spokesperson Nathan Stevens said: “While our firefighters deal with incidents that are visible to the public, our 999 emergency control operators often go unseen, yet do a vital job.
"The heatwave has caused a significant increase in the number of calls they have handled.”
Meanwhile, Sherwood police, who cover Ollerton, Clipstone and surrounding villages, have reiterated a message about the danger of starting fires deliberately.
A Facebook post read: “Even small fires can spread very quickly. What may have been intended as a small fire or just a bit of fun can become out of control.
"Each year, the fire service attends about 2,000 deliberate fires. These range from fires in bins and skips to grasslands, fields, barns and haystacks.”