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
The latest bronze tribute to Cristiano Ronaldo took a hammering on social media after it was unveiled at Madeira Airport on Wednesday.
Festival Organisers released another 88 acts on the line-up set to appear in Somerset this June, including Stormzy, The XX and The National.
The new sugar targets are being introduced in an effort to tackle childhood obesity as a third of children are leaving school overweight.