Two teenagers have been arrested on suspicion of assault after a school was plunged into lockdown "as a precaution".
Hundreds of parents have rushed to the gates of Manor Community Academy, on Owton Manor Lane, Hartlepool after being told to collect their children.
Alarms could be heard sounding after classrooms were locked around 11.15am. Students reported "teachers bleeding and crying".
Parents are being told they must come to school to collect their children. One witness says: "There are kids crying and everything. It's really bad."
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