A teenage girl was rescued when fire broke out at an old farm building in Ripley.
Emergency services attended the blaze off Coach Road at 6.15pm on Tuesday.
They rescued the 18-year-old girl from the building.
She was taken to the Royal Derby Hospital to be treated for smoke inhalation.
A 17-year-old girl, an 18-year-old girl and a 20-year-old man have been arrested on suspicion of arson with intent to endanger life and remain in police custody.
Witnesses or anyone with information should call Derbyshire police, quoting incident number 567 of April 19.