Four teenagers have been arrested in connection with the fire at the Darul Uloom School in Chislehurst, south-east London on Saturday night, Scotland Yard said.
Two 17-year-olds and two 18-year-old were arrested on suspicion of arson late yesterday and taken into custody.
Bromley Borough police officers are continuing to establish the full circumstances of the fire.
More than 100 pupils and staff at the Islamic boarding school had to be evacuated when the fire broke out.
More top news
Kim Dick spoke about her fears as she comforted a young Manchester Arena victim as she waited anxiously for news of her own family.
"Nobody does it better," the current James Bond Daniel Craig said in a tribute to his predecessor.
Thousands of troops could be sent out to protect key sites and events after the Manchester attack. Here's everything you need to know.