More than 500 acres of moorland in the Yorkshire Dales have been destroyed by a blaze which experts predict could affect up to 70% of the moor.
Firefighters expect to be at the scene for several more days
The fire on Ilkley Moor, which began last Wednesday, is thought to have had a devastating impact on wildlife.
Firefighters have the blaze under control but expect to be at the scene for several more days.
It is thought the fire could have been caused by a discarded match or cigarette, a spokesman said.
The spokesman for West Yorkshire Fire Service said: "It's a very large fire which is smouldering away so it's extremely long, labour-intensive and hot work.
"It's not uncommon at all for fires on moorland to go on for days, or even weeks."
A Moorland Association spokeswoman warned neighbouring moors were also at risk and said there were also risks to opening up the moorland under the Countryside Rights of Way (Crow) Act - often referred to as the right to roam.
She said: "There were risks to opening up these vast tracts of moorland.
"We need to get the message out that it's not a good idea to be up on the moors when they're on fire."
But a spokesman for the Countryside Agency said: "Ilkley Moor has been open for hundreds of years. To say this has been caused by the Crow Act is mixing the issues."