AVON Fire & Rescue Service has carried out an investigation into the fire at Yatton Infant School on Monday, which caused “significant” damage.
Firefighters from across the district were called to the scene at 1.18pm.
Police closed the village's High Street while efforts to extinguish the fire were underway.
Today, a fire service spokesperson said: “Following fire investigation on May 30, the cause of the fire is thought to be accidental.”
In an earlier update, they said: “Crews from across the service were mobilised to the incident and on arrival found a significant fire affecting the school site.
“Over the course of the afternoon, crews from Clevedon, Weston, Blagdon, Nailsea, Avonmouth, Kingswood, Temple, Yate, Portishead and Bedminster attended the scene.
“The area was sectorised, with nine fire engines, two turntable ladders and a command unit all in attendance at the height of the incident.
“The High Street was closed for some time by police colleagues to allow for crews to work safely at the scene, but has since reopened.
“This is obviously devastating for the school and local community, and we wish them all the best over the coming weeks which will be difficult for staff, parents and pupils.”
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