It is thought a fire which has damaged a large area of woodland in Lincolnshire was started deliberately.
Crews were called to Stapleford woods near Lincoln at 1800 BST on Saturday.
Firefighters spent much of Sunday damping down and used thermal imaging cameras to find pockets of fire still burning in the undergrowth.
It is thought around 1,000 square metres have been damaged and many trees may have to be felled.
Badly burned
Divisional Officer Mike Sinnatt felt it is likely to have been started on purpose.
He said: "It could have been accidental, a discarded cigarette or something of that sort.
"I tend to think it is more likely to have been malicious because there are no footpaths through the area.
"It is about 100 metres to the nearest footpath where the bulk of the burning is so I suspect it was malicious."
He added: "Quite a number of mature trees are badly burned around the base, which I think will kill them.
"The bark has been burnt off and the sap wood is charred which basically cuts off their food supply.
"I would imagine a number of trees will have to be felled."