Residents fled from a house blaze in Corby which was tackled by 20 firefighters.
The fire broke out last night in the three-storey building in Westminster Walk, which had been converted into flats.
A bedroom was destroyed and there was smoke damage to other rooms.
Firefighters said flats on the second floor of the building were also damaged by smoke.
Firefighters from Corby, Kettering and Desborough were called to the scene shortly after 9.40pm.
The worst of the fire was contained in one room as the door was shut.
Fire crews confirmed there were people in the flat at the time of the blaze but said that they had a lucky escape and got out without being injured.
A spokesman for Northamptonshire Fire and Rescue service said: "The fire was contained in one bedroom because the door was shut but the damage is quite bad.
"In fact the bedroom has been completely destroyed.
"It's quite visible from the outside because there is quite a lot of black staining.
The Fire Service, the police and the Arson Task Force visited the scene today to investigate how the blaze started.
The investigation revealed the cause was not suspicious.