A "devastating" fire which spread across 200 acres of moorland was started by a camp fire, a fire service said.
Investigators found a fire pit created out of rocks thought to have been left by people camping in the area.
They found an out of control camp fire had spread across the Roaches, in Upper Hulme, Staffordshire.
The area has been "destroyed" by the fire, Staffordshire Fire and Rescue Service said.
It is believed the campers attempted to extinguish the fire by covering it with rocks, but this was not enough to stop it from spreading.
Glynn Luznyj, from Staffordshire Fire Service, said it is "very frustrating that it [the fire] could have been easily prevented".
Crews have been at the fire scene since 9 August.
Staffordshire Wildlife Trust said it had been "devastating" for wildlife.
The trust, which runs the Roaches, has already noticed displacement of animals and said the blaze has caused "a huge loss of habitat".
The fire, which is still not completely extinguished, has been "extremely difficult for firefighters", he said, and crews will remain at the scene "for the next couple of days".
"The heatwave has made everything extremely dry and flammable, which no doubt contributed to the quick spread of this blaze along with the strong winds," Mr Luznyj said.
Several people had to be evacuated from their homes due to the fire and one man had to treated for smoke inhalation.
On Wednesday, the fire service said the number of deliberate grass fires in Staffordshire had quadrupled, with crews being called to tackle 323 deliberate fires within the first three weeks of the school holidays.