The bill for extra security measures at a fire-hit derelict school is expected to be £25,000.
Flames ripped through the former Kingswood School site, in Gainsborough Road, Corby, in the early hours of Saturday.
The complex has been standing empty since the summer of 2010 when staff and pupils moved to a new £26m school on a neighbouring site.
A spokesman for Northamptonshire County Council said: “It had been the authority’s intention to demolish the buildings prior to selling the site and a planning application to that effect has been submitted.
“We will now concentrate on securing the site and making it safe.
“At this stage it is still too early to say exactly what the financial implications of the fire are but realistically we would anticipate it costing in the region of £25,000 for extra security and security repairs at the site of the former school.”
The fire service is still investigating the cause of the blaze.
Eight fire engines attended the incident after being called just after 1am and crews stayed at the scene for three hours while firefighters tackled the blaze.
It is believed the fire started in the former school’s science block.
The top floor of the building has been completely destroyed and the ground floor has been severely damaged by water.
Two fire crews stayed at the school during Saturday to ensure the area was safe.
At its height there were 50 firefighters at the scene, with pumps attending from Corby, Kettering, Desborough, Rothwell, Market Harborough, Burton Latimer, Thrapston, Daventry and Northampton.
The building’s roof has completely burned away in some places but the fire did not spread to any other blocks.
The new Kingswood School building, which sits next to the old site, was not affected by the blaze.
A spokesman for the fire service said: “The block is devastated but luckily the fire didn’t spread.
“We need a structural engineer to assess the site and after it has been made safe we will begin the investigation.”
The spokesman added an assessment of the site will probably take place this week with fire and police officers hoping to determine the cause of the blaze.