Four teenagers have been arrested on suspicion of arson in connection with a fire at an Islamic boarding school in Chislehurst, south east London, Scotland Yard said.
Scotland Yard said the two 17-year-olds and two 18-year-olds were detained late last night and taken to a south London police station, where they remain in custody.
Almost 130 pupils and staff were evacuated from the Darul Uloom Islamic School in Chislehurst, south-east London, last night with teachers reacting quickly and extinguishing the flames.
Only minor damage was caused to the school but two boys suffered from smoke inhalation though they were not taken to hospital.
School principal Mustafa Musa said: "We would like to show our appreciation to the police, fire and ambulance services and well-wishers who have responded and offered support in this time of need.
"The parents should rest assured that the students are safe and have been well looked after.
"The academic department of the school was set alight just before midnight by intruders.
"Initially the staff extinguished the fire and evacuated the students to safety.
"The fire and ambulance services responded rapidly and ensured no one was seriously injured.
"Two boys suffered smoke inhalation injuries but thank God they are recovering.
"We are part of the British community and are deeply saddened by the events that have taken place.
"We urge the community to stay firm and united and bring the people responsible to justice.
"The community at large have to come together for a safe and peaceful life in Britain."
The fire whappened only days after an Islamic centre in London's Muswell Hill was burnt to the ground amid allegations it was a racist attack.
The building was daubed with the letters ''EDL'', apparently referencing the English Defence League.
On Sunday night, Metropolitan Police commissioner Bernard Hogan-Howe said: "These are difficult times for London's communities.
"The Met is now investigating suspicious fires at two locations within the Islamic community which have happened in the past few days. Fortunately no one has been hurt, but we know that fires can often prove fatal.
"So I want to reassure people that we are using our full range of policing tactics to protect sites that might be vulnerable.
"In all boroughs across London, there is an increased police presence around locations that might be at risk.
"We will maintain a 24/7 guard of uniformed officers at sites we consider to be at greatest risk.
"Detectives are working tirelessly to establish whether these fires were started deliberately, and if so, to catch those responsible.
"We should not allow the murder of Lee Rigby to come between Londoners.
"The unified response we have seen to his death across all communities will triumph over those who seek to divide us."
London Fire Brigade said the fire was under control in less than an hour after being called.
The £3,000-a-year boarding school was established in 1988 with the purpose of producing "great scholars and Huffaz (people who have memorised the Koran) to preserve and transmit the eternal message of Allah".
Its website says: "The institution helps children to explore and develop their Islamic identity as a natural part of their mental, emotional and personal development.
"The school aims to prepare Muslim students to be good Muslims and responsible citizens; to embed in the student a sense of discipline; to enable them to grow up to become upright, respectable and worthy citizens of their respective countries."
The school was built in 1974 and comprises 130 boarding rooms in addition to classrooms, dining hall, assembly hall, prayer hall, gym, playing fields and car parking with 100 spaces, over a 10 acre site.
An extension was built in 2007 consisting of 18 classrooms, a science laboratory, a prayer hall and wudhu (ablution) facilities.