Youths who lit a fire in the fireplace of the disused former Northamptonshire Association for the Blind (NAB) building in Northampton are believed to be responsible for the large blaze which severely damaged the premises.
Firefighters were called to Wardington Court, in Welford Road, shortly after 1am on Friday after large flames were seen coming out of the roof of the building, which is due to be converted into flats for elderly people.
An investigation has now taken place into the cause of the fire, and concluded it was probably started accidently by some young people who had got into the building and started a fire in the fireplace, which then got out of control.
A spokesman for Northants Fire & Rescue Service said: “What we think happened is that youths lit a fire in the old fireplace of the building.
“We do not think they did it deliberately but the fire spread from the fireplace.”
The NAB building, which was built in about 1860, is currently being converted into 41 one-bedroom and 17 two-bedroom apartments for elderly people. The work is being carried out by McCarthy & Stone, and part of the building is due to be demolished.
A spokesman for McCarthy & Stone said a structural engineer will be visiting the site this week to assess the building.
A section of Welford Road was closed for several hours due to the fire.