A teenage girl has been arrested on suspicion of arson with intent to endanger life over the Millais School fire in Horsham.
The 16-year-old was arrested yesterday and was interviewed and bailed before being rearrested this morning as a result of further information.
Sussex Police have not confirmed whether or not the teen was a pupil.
Chief Inspector Howard Hodges, Horsham District Commander said: "This investigation remains focussed on establishing the sequence of events that led to the fire at Millais School.
"I want to reassure the pupils, parents, school and wider Horsham communities that this investigation will establish the truth of what happened that day.
"We continue to work closely with the school to ensure that our investigation compliments the significant efforts that the school is making to return to normality at the earliest opportunity.
"It is important that the investigation is allowed to progress and I would ask that rumour and speculation via social media or other avenues - whilst understandable in the circumstances - are avoided to ensure the integrity of our investigation.
"I would like to appeal again to anyone with information that may help us in our investigation to contact police 101, email email@example.com or call the independent charity Crimestoppers anonymously on 0800 555 111. "
Alex Osuch captured the fire on video.