Aerial images show firefighters continuing to battle a peatland fire which started 11 days ago.
The fire at Holme Fen near Peterborough involves an area measuring around 60 football pitches and is deep seated in peat, Cambridgeshire Fire and Rescue Service said last week.
Peat is formed over thousands of years by the partial decomposition of organic matter, mainly plant material, in wetlands.
Peat fires can spread underground and are “notoriously difficult to extinguish”, the Wildlife Trust for Bedfordshire, Cambridgeshire and Northamptonshire said on its website for The Great Fen.
It describes Holme Fen as a “thriving nature reserve” which includes Holme Post, which at 2.75 metres below sea level is said to be the lowest land point in Great Britain.
The fire service said crews are expected to remain at the scene “for the foreseeable future” while working to also maintain cover for other emergencies.
The fire started on August 8, with more than 80 firefighters on scene including from neighbouring fire and rescue services during the operation that has followed.
Incident commander Wayne Swales said in an earlier update that vegetation had been on fire as well as peat burning below the ground.
He said crews were dealing with “fires above ground, fires below ground” and described the fire as “challenging”.
Firefighters have been checking for hotspots and dampening down the area, and advising people who are still seeing or smelling smoke in the area that it is “likely still coming from Holme Fen”.
Matt Jackson, conservation director at the Wildlife Trust for Bedfordshire, Cambridgeshire and Northamptonshire, said recent wildfires have been a “stark wake-up call”.
He said: “We must invest in climate resilience if we are to tackle the impacts prolonged heatwaves and drought are having on landscapes, nature and communities across the UK.
“This means working to restore and protect our natural infrastructure, including wetlands and peatlands – which act as sponges, storing carbon and holding water in our landscapes, and reversing decades of drainage impacts to make them less flammable in years to come.”
He said the trust is working to restore peatlands and raise water levels to “build natural resilience and tackle the threat of wildfire”.