A secondary school in South Wales went into 'lock-down' when a balaclava-clad teenager carrying a knife roamed the building.
Mountain Ash Comprehensive School, Rhondda Cynon Taf, was put on high alert after the 16-year-old was seen carrying the 'small knife' before staff chased him off the site.
He spent 10 minutes wandering around the school while pupils stayed in their classrooms.
No one was hurt in the incident and staff at the school have been praised for their 'brave and swift' response in protecting their students.
South Wales Police confirmed that officers were sent to the school at 11.15am on Monday and a teenager remains in custody after he was arrested outside the school grounds on suspicion of affray.
In a statement on the school's website, headteacher Huw Lloyd said: "As you may be aware through social media, a youth walked in to school around 11.15am wearing a balaclava and carrying a small knife.
"Our own emergency procedures 'kicked in' and the school was locked down to ensure everyone's safety.
"The culprit was ushered off site by our own staff who were in constant communication via our 'walky talky' system. In the meantime, the police emergency response team were called.
"No pupil or staff member was injured in any way and I am reassured by the way our staff, in conjunction with the police, dealt with this incident. The person was on site for barely 10 minutes.
"I would also reassure parents that our site is fully fenced and is as safe as any secondary school in RCT."
Police Inspector Tony Carpenter said: "I'd like to reassure the community – especially parents of children at the school – that we have somebody in custody and that nobody was hurt. We'd like to speak with anybody who we haven't yet spoken to, who saw what happened or who has information."
Police are now appealing for any information about the incident. Details can be shared at South Wales Police's non emergency 101 number, or by calling Crimestoppers anonymously on 0800 555 111.