A teenager has been arrested at a school in Norfolk after threats were posted on an internet website.
The boy, aged 16, was arrested at Attleborough High School, Attleborough, at 1130 GMT.
Norfolk Police said officers seized a knife, matches and a canister of what is believed to be a flammable liquid.
The boy has been arrested on suspicion of threats to commit criminal damage and possession of an offensive weapon. He is currently in custody.
Supt Katie Elliott said: "The constabulary was alerted by a member of the public after a message was posted on a website inferring the criminal damage to Attleborough School."
Police said all pupils had their bags searched as a precaution.
Nothing further was found at the school, which was searched with the help of teaching staff, said the police.
The youth's home address has been searched and a computer has been seized which is currently being analysed.
The youth remains in custody and will be interviewed on Tuesday night and on Wednesday.