Police are treating a fire at a former school in Porthcawl as deliberate.
Emergency services were called in the early hours of Saturday and flames could be seen for miles around.
A spokesman for South Wales Police said the fire in a derelict building in Church Street, which is an old school, left the structure seriously damaged.He added: "It is believed that the fire was started deliberately."
The building used to house St John’s School until it merged with the neighbouring St Clare’s School in 2014.
A planning application is due to be submitted to demolish the existing buildings and replace it with 74 homes.
Police were notified by the fire service at approximately 1.30am.
A joint investigation between South Wales Police and South Wales Fire and Rescue Service is now under way.
Anybody with information about the incident is asked to contact 101 quoting reference *198598.
Alternatively they can contact Crimestoppers anonymously on 0800 555 111.
