Firefighters tackled a blaze in a derelict building possibly used by rough sleepers.
Crews were called to Devon Drive, Mansfield, at about 7am today and used a variety of gear to extinguish the blaze in the building.
A Derbyshire fire service spokesman said: "The fire was in the roof space and was out by 8.15am.
"We believe that the cause of the fire was a heat source - believed to be a match - being brought together with combustible items, although it's not known who did this.
"At this stage, we're not sure if this was an intentional fire.
"It looks like people may have been sleeping rough in the building."
There were no reports of any injuries.