Emergency services were called to the former Moira House School in Upper Carlisle Road on October 19, 2025.
Eight fire engines were used to tackle the blaze but police were unable to find the cause of the fire.
A spokesperson for Sussex Police said: “Following a thorough investigation and engagement with East Sussex Fire and Rescue (ESFRS), it was not possible to establish the exact cause of the fire.”
The historic girls school, which closed in 2020, was set to be developed into 33 apartments and 19 houses. It received planning permission in 2022 and work had begun late last year (2024).
When it initially happened he said: “It’s just terrible. We’ll definitely lose the school house, which is a real tragedy.
"It’s made me feel incredibly sad about the whole thing.
"We’ve met so many people who went to school there and it means an awful lot to them.
"When you talk to people, you completely get how the community is affected like this.”
See in photos the damage and aftermath of the fire.
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Crews from East Sussex Fire and Rescue alongside Sussex Police were called to the former Moira House School in Upper Carlisle Road at 5.47pm on Sunday, October 19. Picture: Staff Photo: Staff
6. Emergency services called to tackle blaze at former Eastbourne school
Emergency services called to tackle blaze at former Eastbourne school Photo: Staff
7. Emergency services called to tackle blaze at former Eastbourne school
Emergency services called to tackle blaze at former Eastbourne school Photo: Staff
8. Emergency services called to tackle blaze at former Eastbourne school
Emergency services called to tackle blaze at former Eastbourne school Photo: Staff